Fastly (FSLY) 10-Q 9 Aug 19 2019 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2019	Aug. 07, 2019
Entity Listings [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2019
Document Transition Report	false
Entity File Number	001-38897
Entity Registrant Name	FASTLY, INC.
Entity Central Index Key	0001517413
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-5411834
Entity Address, Address Line One	475 Brannan Street, Suite 300
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94107
City Area Code	844
Local Phone Number	432-7859
Title of 12(b) Security	Class A Common Stock, $0.00002 par value
Trading Symbol	FSLY
Security Exchange Name	NYSE
Entity Current Reporting Status	No
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Common Class A
Entity Listings [Line Items]
Entity Common Stock, Shares Outstanding		13,036,488
Common Class B
Entity Listings [Line Items]
Entity Common Stock, Shares Outstanding		80,433,917

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 213,463	$ 36,963
Marketable securities	32,156	46,679
Accounts receivable, net of allowance for doubtful accounts of $1,525 and $1,679 as of June 30, 2019 and December 31, 2018, respectively	28,542	24,729
Prepaid expenses and other current assets	12,192	8,896
Total current assets	286,353	117,267
Property and equipment, net	55,610	42,354
Goodwill	359	360
Intangible assets, net	1,198	610
Other assets	12,856	2,163
Total assets	356,376	162,754
Current liabilities:
Accounts payable	5,753	2,333
Accrued expenses	25,101	15,535
Current portion of long-term debt	32,822	11,370
Other current liabilities	1,589	2,512
Total current liabilities	65,265	31,750
Long-term debt, less current portion	17,878	39,439
Convertible preferred stock warrant liabilities	0	3,261
Other long-term liabilities	5,911	647
Total liabilities	89,054	75,097
Commitments and contingencies (Note 9)
Convertible preferred stock	0	219,584
Stockholders’ equity (deficit):
Class A and Class B common stock	2	1
Additional paid-in capital	435,189	16,403
Treasury stock	(2,109)	(2,109)
Accumulated other comprehensive income (loss)	13	(36)
Accumulated deficit	(165,773)	(146,186)
Total stockholders’ equity (deficit)	267,322	(131,927)
Total liabilities, convertible preferred stock, and stockholders’ equity (deficit)	$ 356,376	$ 162,754

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 1,525	$ 1,679

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Revenue	$ 46,173,000	$ 34,448,000	$ 91,729,000	$ 66,946,000
Cost of revenue	20,784,000	15,695,000	40,502,000	31,079,000
Gross profit	25,389,000	18,753,000	51,227,000	35,867,000
Operating expenses:
Research and development	11,244,000	8,099,000	21,420,000	16,078,000
Sales and marketing	16,906,000	11,973,000	31,945,000	24,316,000
General and administrative	8,920,000	4,130,000	17,620,000	9,832,000
Total operating expenses	37,070,000	24,202,000	70,985,000	50,226,000
Loss from operations	(11,681,000)	(5,449,000)	(19,758,000)	(14,359,000)
Interest income	861,000	147,000	1,277,000	284,000
Interest expense	(2,989,000)	(359,000)	(4,224,000)	(740,000)
Other expense, net	(1,696,000)	(140,000)	(2,472,000)	(234,000)
Loss before income taxes	(15,505,000)	(5,801,000)	(25,177,000)	(15,049,000)
Income taxes	82,000	35,000	137,000	93,000
Net loss	(15,587,000)	(5,836,000)	(25,314,000)	(15,142,000)
Other comprehensive (loss) income:
Foreign currency translation adjustment	(21,000)	(46,000)	7,000	16,000
Loss on investments in available-for-sale-securities	14,000	8,000	42,000	6,000
Total other comprehensive (loss) income	(7,000)	(38,000)	49,000	22,000
Comprehensive loss	(15,594,000)	(5,874,000)	(25,265,000)	(15,120,000)
Net loss attributable to common stockholders	$ (15,587,000)	$ (5,836,000)	$ (25,314,000)	$ (15,142,000)
Net loss per share attributable to common stockholders, basic and diluted (USD per share)	$ (0.26)	$ (0.24)	$ (0.59)	$ (0.63)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	59,781	24,127	42,599	24,034

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Class A	Common Class B	Convertible Preferred Stock	Common Stock	Common StockCommon Class A	Common StockCommon Class B	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Convertible Preferred Stock, beginning balance (in shares) at Dec. 31, 2017				49,718,084
Convertible Preferred Stock, beginning balance at Dec. 31, 2017				$ 179,705
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of stock (in shares)				3,832,362
Issuance of stock				$ 39,063
Convertible Preferred Stock, ending balance (in shares) at Jun. 30, 2018				53,550,446
Convertible Preferred Stock, ending balance at Jun. 30, 2018				$ 218,768
Beginning balance (in shares) at Dec. 31, 2017					23,879,074
Beginning balance at Dec. 31, 2017	$ (107,006)				$ 1			$ 10,377	$ (2,109)	$ (24)	$ (115,251)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of convertible preferred stock to Class B common stock (in shares)			53,600,000
Issuance of Class A common stock in connection with the IPO, net of underwriting discounts (in shares)		12,900,000
Exercise of stock options (in shares)					438,186
Exercise of stock options	692							692
Vesting of early exercised stock options (in shares)					48,266
Vesting of early exercised stock options	70							70
Stock-based compensation	1,838							1,838
Repayment of stockholder note, shares					8,828
Repayment of stockholder note	20							20
Net loss	(15,142)		$ (15,142)								(15,142)
Other comprehensive loss	22									22
Ending balance at Jun. 30, 2018	(119,506)				$ 1			12,997	(2,109)	(2)	(130,393)
Ending balance (in shares) at Jun. 30, 2018					24,374,354
Convertible Preferred Stock, beginning balance (in shares) at Mar. 31, 2018				49,718,084
Convertible Preferred Stock, beginning balance at Mar. 31, 2018				$ 179,705
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of stock (in shares)				3,832,362
Issuance of stock				$ 39,063
Convertible Preferred Stock, ending balance (in shares) at Jun. 30, 2018				53,550,446
Convertible Preferred Stock, ending balance at Jun. 30, 2018				$ 218,768
Beginning balance (in shares) at Mar. 31, 2018					24,035,354
Beginning balance at Mar. 31, 2018	(115,189)				$ 1			11,440	(2,109)	36	(124,557)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)					318,377
Exercise of stock options	517							517
Vesting of early exercised stock options (in shares)					11,795
Vesting of early exercised stock options	30							30
Stock-based compensation	990							990
Repayment of stockholder note, shares					8,828
Repayment of stockholder note	20							20
Net loss	(5,836)		(5,836)								(5,836)
Other comprehensive loss	(38)									(38)
Ending balance at Jun. 30, 2018	(119,506)				$ 1			12,997	(2,109)	(2)	(130,393)
Ending balance (in shares) at Jun. 30, 2018					24,374,354
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact of change in accounting policy	$ 0
Convertible Preferred Stock, beginning balance (in shares) at Dec. 31, 2018	53,630,213			53,630,213
Convertible Preferred Stock, beginning balance at Dec. 31, 2018	$ 219,584			$ 219,584
Increase (Decrease) in Temporary Equity [Roll Forward]
Conversion of convertible preferred stock to Class B common stock (in shares)				(53,630,213)
Conversion of convertible preferred stock to Class B common stock				$ (219,584)
Convertible Preferred Stock, ending balance (in shares) at Jun. 30, 2019	0			0
Convertible Preferred Stock, ending balance at Jun. 30, 2019	$ 0			$ 0
Beginning balance (in shares) at Dec. 31, 2018						0	25,025,836
Beginning balance at Dec. 31, 2018	(131,927)					$ 0	$ 1	16,403	(2,109)	(36)	(146,186)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of convertible preferred stock to Class B common stock (in shares)							53,630,213
Conversion of convertible preferred stock to Class B common stock	219,584						$ 1	219,583
Conversion of convertible preferred stock warrants into Class B common stock warrants	5,665							5,665
Issuance of Class A common stock in connection with the IPO, net of underwriting discounts (in shares)						12,937,500
Issuance of Class A common stock in connection with the IPO, net of underwriting discounts	$ 186,912							186,912
Exercise of stock options (in shares)	1,418,000					57,658	1,211,230
Exercise of stock options	$ 2,532							2,532
Exercise of common stock warrants (in shares)							172,380
Vesting of early exercised stock options (in shares)							81,054
Vesting of early exercised stock options	310							310
Stock-based compensation	3,710							3,710
Repayment of stockholder note, shares							31,939
Repayment of stockholder note	74							74
Net loss	(25,314)	$ (1,931)	(23,383)								(25,314)
Other comprehensive loss	49									49
Ending balance at Jun. 30, 2019	$ 267,322					$ 0	$ 2	435,189	(2,109)	13	(165,773)
Ending balance (in shares) at Jun. 30, 2019						12,995,158	80,152,652
Convertible Preferred Stock, beginning balance (in shares) at Mar. 31, 2019				53,630,213
Convertible Preferred Stock, beginning balance at Mar. 31, 2019				$ 219,584
Increase (Decrease) in Temporary Equity [Roll Forward]
Conversion of convertible preferred stock to Class B common stock (in shares)				(53,630,213)
Conversion of convertible preferred stock to Class B common stock				$ (219,584)
Convertible Preferred Stock, ending balance (in shares) at Jun. 30, 2019	0			0
Convertible Preferred Stock, ending balance at Jun. 30, 2019	$ 0			$ 0
Beginning balance (in shares) at Mar. 31, 2019						0	25,521,408
Beginning balance at Mar. 31, 2019	(133,598)					$ 0	$ 1	18,676	(2,109)	20	(150,186)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of convertible preferred stock to Class B common stock (in shares)							53,630,213
Conversion of convertible preferred stock to Class B common stock	219,584						$ 1	219,583
Conversion of convertible preferred stock warrants into Class B common stock warrants	5,665							5,665
Issuance of Class A common stock in connection with the IPO, net of underwriting discounts (in shares)						12,937,500
Issuance of Class A common stock in connection with the IPO, net of underwriting discounts	186,912							186,912
Exercise of stock options (in shares)						57,658	761,479
Exercise of stock options	1,893							1,893
Exercise of common stock warrants (in shares)							172,380
Vesting of early exercised stock options (in shares)							40,530
Vesting of early exercised stock options	155							155
Stock-based compensation	2,243							2,243
Repayment of stockholder note, shares							26,642
Repayment of stockholder note	62							62
Net loss	(15,587)	$ (1,685)	$ (13,902)								(15,587)
Other comprehensive loss	(7)									(7)
Ending balance at Jun. 30, 2019	267,322					$ 0	$ 2	$ 435,189	$ (2,109)	$ 13	$ (165,773)
Ending balance (in shares) at Jun. 30, 2019						12,995,158	80,152,652
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact of change in accounting policy	$ 5,727

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY (DEFICIT) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Statement of Stockholders' Equity [Abstract]
Stock issuance costs	$ 121	$ 121

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net loss	$ (25,314)	$ (15,142)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	7,624	6,295
Amortization of deferred rent	3,985	(112)
Amortization of debt issuance costs	1,816	0
Stock-based compensation	3,710	1,838
Provision for doubtful accounts	69	276
Other non-operating activities	(400)	(42)
Interest paid on capital leases	(171)	(116)
Change in fair value of preferred stock warrant liabilities	2,404	79
Loss on disposals of property and equipment	39	0
Changes in operating assets and liabilities:
Accounts receivable	(3,882)	(3,375)
Prepaid expenses and other current assets	(3,209)	(1,504)
Other assets	(4,966)	514
Accounts payable	3,270	(1,389)
Accrued expenses	287	(39)
Other liabilities	(910)	133
Net cash used in operating activities	(15,648)	(12,584)
Cash flows from investing activities:
Purchases of marketable securities	(32,662)	(10,657)
Sales of marketable securities	47,634	19,927
Purchases of property and equipment	(9,229)	(9,834)
Purchases of intangible assets	(636)	0
Net cash provided by (used in) investing activities	5,107	(564)
Cash flows from financing activities:
Proceeds from initial public offering, net of underwriting fees	192,510	0
Proceeds from borrowings under notes payable	0	4,000
Repayments of notes payable	(4,988)	0
Repayments of capital leases	(676)	(585)
Proceeds from Series F financing	0	39,184
Proceeds from Employee Stock Purchase Plan	810	0
Proceeds from exercise of vested stock options	2,530	691
Proceeds from early exercise of stock options	520	0
Proceeds from payment of stockholder note	74	20
Repurchase of early exercised shares	0	(13)
Net cash provided by financing activities	187,127	43,176
Effects of exchange rate changes on cash, cash equivalents, and restricted cash	1	9
Net increase in cash, cash equivalents, and restricted cash	176,587	30,037
Cash, cash equivalents, and restricted cash at beginning of period	36,963	31,396
Cash, cash equivalents, and restricted cash at end of period	213,550	61,433
Supplemental disclosure of cash flow information:
Cash paid for interest	4,435	938
Cash paid for income taxes, net of refunds received	13	48
Property and equipment additions not yet paid in cash	8,035	365
Vesting of early-exercised stock options	310	81
Capital lease outstanding from current year addition	3,740	458
Conversion of convertible preferred stock warrants to convertible common stock warrants	5,665	0
Costs related to initial public offering, accrued but not yet paid	1,945	0
Reconciliation of cash, cash equivalents, and restricted cash as shown in the statements of cash flows
Total cash, cash equivalents, and restricted cash	36,963	31,396
IPO
Cash flows from financing activities:
Payments of issuance costs	(3,653)	0
Convertible preferred stock
Cash flows from financing activities:
Payments of issuance costs	$ 0	$ (121)

Nature of Business

Nature of Business	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	Nature of Business Fastly, Inc. has built an edge cloud platform that can process, serve, and secure its customer’s applications as close to their end users as possible. Our edge network spans 64 Points-of-Presence ("POPs") around the world, as of June 30, 2019. We were incorporated in Delaware in 2011 and are headquartered in San Francisco, California. As used herein, "Fastly," "we," "our," "the Company," and similar terms include Fastly, Inc. and its subsidiaries, unless the context indicates otherwise. Stock Split On May 3, 2019, we implemented a 1-for- 2 reverse stock split of our stock. All shares of Common Stock, stock-based instruments, and per-share data included in these financial statements give effect to the stock split and the changes in authorized shares have been adjusted retroactively for all periods presented. Initial Public Offering ("IPO") On May 21, 2019 we completed an IPO in which we sold 12,937,500 shares of our newly authorized Class A common stock, which included 1,687,500 shares sold pursuant to the exercise by the underwriters of an option to purchase additional shares, at the public offering price of $16.00 per share. We received net proceeds of $192.5 million , after deducting underwriting discounts and commissions, from sales of our shares in the IPO. The net proceeds include additional proceeds of $25.1 million , net of underwriters' discounts and commissions, from the exercise of the underwriters' option to purchase an additional 1,687,500 shares of our Class A common stock. Immediately prior to the completion of the IPO, all shares of common stock then outstanding were reclassified as Class B common stock and all shares of convertible preferred stock then outstanding were converted into 53,630,213 shares of common stock on a one

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The interim unaudited condensed consolidated financial statements and accompanying notes have been prepared in accordance with United States generally accepted accounting principles ("U.S. GAAP") along with instructions to Form 10-Q and Article 10 of Securities and Exchange Commission ("SEC") Regulation S-X. Principles of Consolidation The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. Unaudited Interim Financial Statements The accompanying interim condensed consolidated balance sheet as of June 30, 2019 , the related interim condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2019 and 2018 , the condensed consolidated statements of cash flows, the condensed consolidated statements of convertible preferred stock and stockholders' equity (deficit) for the six months ended June 30, 2019 and 2018 , and the related footnote disclosures are unaudited. The unaudited interim condensed consolidated financial statements have been prepared in accordance with U.S. GAAP. In management’s opinion, the unaudited financial statements have been prepared on the same basis as the audited financial statements and include all adjustments, which include only normal recurring adjustments necessary for the fair presentation of our financial position as of June 30, 2019 , our results of operations and comprehensive income for the three and six months ended June 30, 2019 and 2018 , and our statements of cash flows for the six months ended June 30, 2019 and 2018 . The results for the three and six months ended June 30, 2019 are not necessarily indicative of the results expected for the full fiscal year or any other periods. Use of Estimates The preparation of our condensed consolidated financial statements requires us to make estimates, judgments, and assumptions that affect the reported amounts of assets, liabilities, revenue, costs and expenses, and related disclosures. Actual results and outcomes could differ significantly from our estimates, judgments, and assumptions. Significant estimates, judgments, and assumptions used in these financial statements include, but are not limited to, those related to revenue, accounts receivable and related reserves, useful lives and realizability of long-lived assets, income tax reserves, and accounting for stock-based compensation. Estimates are periodically reviewed in light of changes in circumstances, facts, and experience. The effects of material revisions in estimates are reflected in the condensed consolidated financial statements in the period of change and prospectively from the date of the change in estimate. Concentrations of Credit Risk Financial instruments that potentially subject us to significant concentration of credit risk consist primarily of cash, cash equivalents, marketable securities, and accounts receivable. The primary focus of our investment strategy is to preserve capital and meet liquidity requirements. Our investment policy addresses the level of credit exposure by limiting the concentration in any one corporate issuer or sector and establishing a minimum allowable credit rating. To manage the risk exposure, we invest cash equivalents and marketable securities in a variety of fixed income securities, including government and investment-grade debt securities, and money market funds. We place our cash primarily in checking and money market accounts with reputable financial institutions. Deposits held with these financial institutions may exceed the amount of insurance provided on such deposits, if any. Concentrations of credit risk with respect to accounts receivable are primarily limited to certain customers to which we make substantial sales. Our customer base consists of a large number of geographically dispersed customers diversified across several industries. To reduce risk, we routinely assess the financial strength of our customers. Based on such assessments, we believe that our accounts receivable credit risk exposure is limited. No customer accounted for more than 10% of revenue for the three and six months ended June 30, 2019 and 2018 or more than 10% of the total accounts receivable balance as of June 30, 2019 and December 31, 2018 . Significant Accounting Policies There have been no material changes to our significant accounting policies as compared to those described in the Final Prospectus dated May 16, 2019 relating to our IPO, filed with the SEC pursuant to Rule 424(b) under the Securities Act of 1933, as amended (the "Prospectus"). Recently Adopted Accounting Pronouncements In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASU 2014-09"), which amends the existing accounting standards for revenue recognition, Topic 605, and outlines a single set of comprehensive principles for recognizing revenue under U.S. GAAP. Among other things ASU 2014-09 requires entities to assess the products or services promised in contracts with customers at contract inception to determine the appropriate unit at which to record revenue, which is referred to as a performance obligation. Revenue is recognized when or as control of the promised products or services is transferred to customers at an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those products or services. We have adopted ASU 2014-09 as of January 1, 2019 using the modified retrospective method applied to those contracts which were not completed as of January 1, 2019. Revenues and contract assets or liabilities for contracts completed prior to January 1, 2019 are presented under Topic 605, and revenues and contract assets and liabilities from contracts which were not completed or started after December 31, 2018 are presented under Topic 606. We recorded a net increase in stockholders’ equity (retained earnings) of $5.7 million as of January 1, 2019 due to the cumulative impact of adopting Topic 606 and Topic 340, Other Assets and Deferred Costs. Refer to Note 3, "Revenue" , in the Notes to the Condensed Consolidated Financial Statements for further information. In August 2016, FASB issued Accounting Standards Update No. 2016-15, Statement of Cash Flows (Topic 230) Classification of Certain Cash Receipts and Cash Payments ("ASU 2016-15"), which clarifies how entities should classify cash receipts and cash payments related to eight specific cash flow matters on the statement of cash flows, with the objective of reducing existing diversity in practice. ASU 2016-15 designates the appropriate class flow classification, including requirements to allocate certain components of these cash receipts and payments among operating, investing, and financing activities. The guidance is effective for financial statements issued for fiscal years beginning after December 15, 2018. We adopted this guidance effective January 1, 2019 using the retrospective transition approach for all periods presented. The adoption of ASU 2016-15 did not have a material impact on our condensed consolidated financial statements. In November 2016, the FASB issued Accounting Standards Update No. 2016-18, Statement of Cash Flows (Topic 230) ("ASU 2016-18"), which requires companies to include amounts generally described as restricted cash and restricted cash equivalents in cash and cash equivalents when reconciling beginning-of-period and end-of-period total amounts shown on the statement of cash flows. We adopted this guidance effective January 1, 2019, using the retrospective transition approach for all periods presented. The adoption of ASU 2016-18 did not have a material impact on our condensed consolidated financial statements. In January 2017, the FASB issued Accounting Standards Update No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business ("ASU 2017-01"), which changes the definition of a business to assist entities with evaluating whether transactions should be accounted for as transfers of assets or business combinations. The guidance is effective for financial statements issued for fiscal years beginning after December 15, 2018. We adopted this guidance effective January 1, 2019, using the prospective approach. The adoption of ASU 2017-01 did not have a material impact on our condensed consolidated financial statements. In January 2017, the FASB issued Accounting Standards Update No. 2017-04 , Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment ("ASU 2017-04"), which eliminates step two from the goodwill impairment test. Under this guidance, an entity should recognize an impairment charge for the amount by which the carrying amount of a reporting unit exceeds its fair value up to the amount of goodwill allocated to that reporting unit. The guidance is effective for financial statements issued for fiscal years beginning after December 15, 2020, although early adoption is permitted for annual and interim goodwill impairment testing dates following January 1, 2017. We have elected to early adopt this guidance beginning in the second quarter of 2019 using the prospective method. The adoption of ASU 2017-04 did not have a material impact on our condensed consolidated financial statements. In June 2018, the FASB issued Accounting Standards Update No. 2018-07, Improvements to Nonemployee Share-Based Payment Accounting ("ASU 2018-07"), which simplifies the accounting for share-based payments granted to nonemployees for goods and services. Under ASU 2018-07, certain guidance such as payments to nonemployees would be aligned with the requirements for share-based payments granted to employees. The guidance is effective for fiscal years beginning after December 15, 2019, and interim periods within that fiscal year, although early adoption is permitted. We have elected to early adopt the guidance beginning January 1, 2019. The adoption of ASU 2018-07 did not have a material impact on our condensed consolidated financial statements. Recently Issued Accounting Standards We qualify as an "emerging growth company" as defined in the Jumpstart Our Business Startups Act of 2012 ("JOBS Act") and therefore have elected to continue to take advantage of certain exemptions from various public company reporting requirements, including delaying adoption of new or revised accounting standards until those standards apply to private companies. We have elected to use this extended transition period under the JOBS Act. The effective dates shown below reflect the election to use the extended transition period. In February 2016, the FASB issued new guidance, Accounting Standard Update No. 2016-02, Leases (Topic 842) ("ASU 2016-02"), which establishes the principles to report transparent and economically neutral information about the assets and liabilities that arise from leases. Accordingly, this new standard introduces a lessee model that brings most operating leases on the balance sheet and also aligns certain of the underlying principles of the new lessor model with those in the new revenue recognition standard. The guidance is effective for financial statements issued for fiscal years beginning after December 15, 2019 using the modified retrospective method, although the optional transition method can also be applied. We are currently evaluating the appropriate transition method and impact of this guidance on our condensed consolidated financial statements and related disclosures.

Revenue

Revenue	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Adoption of ASC Topic 606, "Revenue from Contracts with Customers" On January 1, 2019, we adopted ASU 2014-09, Revenue from Contracts with Customers, which replaced the existing revenue recognition guidance, ASC 605, and outlines a single set of comprehensive principles for recognizing revenue under U.S. GAAP. Under Topic 606, revenue is recognized when control of the promised goods or services is transferred to our customers, in an amount that reflects the consideration we expect to be entitled to in exchange for those goods or services. We determine revenue recognition through the following five-step approach: • identification of the contract, or contracts, with a customer; • identification of the performance obligations in the contract; • determination of the transaction price; • allocation of the transaction price to the performance obligations in the contract; and • recognition of revenue when, or as, we satisfy a performance obligation. We adopted ASU 2014-09 using the modified retrospective method applied to those contracts which were not completed as of January 1, 2019. Results for reporting periods beginning after January 1, 2019 are presented under Topic 606, while prior period amounts are not adjusted, and continue to be reported in accordance with our historical accounting under Topic 605. We recorded a cumulative catch-up adjustment to the opening retained earnings of $5.7 million , as of January 1, 2019, due to the cumulative impact of adopting Topic 606 and Topic 340, Other Assets and Deferred Costs. The area impacted was related to the treatment of incremental costs of obtaining contracts with customers. The impact from applying Topic 606 and Topic 340 as of and for the three and six months ended June 30, 2019 is as follows: Condensed Consolidated Statements of Operations Three Months Ended June 30, 2019 Six months ended June 30, 2019 As currently reported Impact of adopting new revenue standards As would have been reported under previous revenue standards As currently reported Impact of adopting new revenue standards As would have been reported under previous revenue standards (in thousands) Sales and marketing $ 16,906 $ (4 ) $ 16,902 $ 31,945 $ 67 $ 32,012 Total operating expenses 37,070 (4 ) 37,066 70,985 67 71,052 Loss from operations (11,681 ) 4 (11,677 ) (19,758 ) (67 ) (19,825 ) Loss before income taxes (15,505 ) 4 (15,501 ) (25,177 ) (67 ) (25,244 ) Net loss (15,587 ) 4 (15,583 ) (25,314 ) (67 ) (25,381 ) Comprehensive loss (15,594 ) 4 (15,590 ) (25,265 ) (67 ) (25,332 ) Net loss attributable to common stockholders $ (15,587 ) $ 4 $ (15,583 ) $ (25,314 ) $ (67 ) $ (25,381 ) Condensed Consolidated Balance Sheets As of June 30, 2019 As currently reported Impact of adopting new revenue standards As would have been reported under previous revenue standards (in thousands) Other assets $ 12,856 $ (5,794 ) $ 7,062 Total assets 356,376 (5,794 ) 350,582 Accumulated deficit (165,773 ) (5,794 ) (171,567 ) Total stockholders’ equity 267,322 (5,794 ) 261,528 Total liabilities and stockholders’ equity $ 356,376 $ (5,794 ) $ 350,582 Revenue recognition Revenue is recognized upon transfer of control of promised products or services to customers in an amount that reflects the consideration we expect to receive in exchange for those products or services. We enter into contracts that can include various combinations of products and services, each of which are distinct and accounted for as separate performance obligations. Revenue is recognized net of any taxes collected from customers, which are subsequently remitted to governmental authorities. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in Topic 606. Our contracts with customers often include promises to transfer multiple products and services to a customer. Determining whether products and services are considered distinct performance obligations that should be accounted for separately versus together may require significant judgment. For contracts with multiple performance obligations, we allocate the contract transaction price to each performance obligation using our estimate of the standalone selling price ("SSP") of each distinct good or service in the contract. Judgment is required to determine the SSP for each distinct performance obligation. We analyze separate sales of our products and services as a basis for estimating the SSP of our products and services. We then use that SSP as the basis for allocating the transaction price when our product and services are sold together in a contract with multiple performance obligations. In instances where SSP is not directly observable, such as when we do not sell the product or service separately, we determine the SSP using information that may include market conditions and other observable inputs. We typically have more than one SSP for individual products and services due to the stratification of those products and services by customers and circumstances. In these instances, we may use information such geographic region and distribution channel in determining the SSP. The transaction price in a contract is typically equal to the minimum commit price in the contract less any discounts provided. Because our typical contracts represent distinct services delivered over time with the same pattern of transfer to the customer, usage-based consideration primarily related to actual consumption over the minimum commit levels is allocated to the period to which it relates. The amount of consideration recognized for usage above the minimum commit price is limited to the amount we expect to be entitled to receive in exchange for providing services. We have elected to apply the practical expedient for estimating and disclosing the variable consideration when variable consideration is allocated entirely to a wholly unsatisfied performance obligation or to a wholly unsatisfied promise to transfer a distinct good or service that forms part of a single performance obligation from our remaining performance obligations under these contracts. Performance obligations represent stand-ready obligations that are satisfied over time as the customer simultaneously receives and consumes the benefits provided by us. These obligations can be content delivery, security, professional services, support, edge cloud platform services, and others. Accordingly, our revenue is recognized over time, consistent with the pattern of benefit provided to the customer over the term of the agreement. At times, customers may request changes that either amend, replace, or cancel existing contracts. Judgment is required to determine whether the specific facts and circumstances within the contracts should be accounted for as a separate contract or as a modification. In contracts where there are timing differences between when we transfer a promised good or service to the customer and when the customer pays for that good or service, we have determined our contracts do not include a significant financing component. We have also elected the practical expedient to not measure financing components for any contract where the timing difference is less than one year. From time to time we enter into arrangements to establish and run private POPs for customers. These arrangements include content delivery services as well as professional services and the provision of hardware. For accounting purposes, we have determined that the provisioning of hardware is an operating lease. We recognize the revenue from these leases monthly on a straight-line basis over the term of the relevant customer agreements. Nature of products and services We primarily derive revenue from the sale of services to customers executing contracts in which the standard contract term is one year, although terms may vary by contract. Most of our contracts are non-cancelable over the contractual term. These contracts can commit the customer to a minimum monthly level of usage and specify the rate at which the customer must pay for actual usage above the monthly minimum. Revenue by geography is based on the billing address of the customer. The following table presents our net revenue by geographic region: Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 (in thousands) United States $ 32,521 $ 26,901 $ 65,943 $ 52,242 All other countries 13,652 7,547 25,786 14,704 Total revenue $ 46,173 $ 34,448 $ 91,729 $ 66,946 Our revenue includes a subset of customers who have leveraged our platform substantially from a usage standpoint. These enterprise customers are defined as customers with revenue in excess of $100,000 over the previous 12-month period. The following table presents our net revenue for enterprise and non-enterprise customers: Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 (in thousands) Enterprise customers $ 39,421 $ 27,872 $ 78,465 $ 55,019 Non-enterprise customers 6,752 6,576 13,264 11,927 Total revenue $ 46,173 $ 34,448 $ 91,729 $ 66,946 Contract balances The timing of revenue recognition may differ from the timing of invoicing to customers. We have an unconditional right to consideration when we invoice our customers and record a receivable. We record a contract asset when revenue is recognized prior to invoicing, or a contract liability (deferred revenue) when revenue is recognized subsequent to invoicing. Deferred revenue includes amounts billed to customers for which revenue has not been recognized and consists of the unearned portions of edge cloud platform usage and Web Application Firewalls ("WAF") security tuning services. Payment terms and conditions vary by contract type, but our standard terms are that payments are due within 15 days from the date of invoice. The following tables present our contract assets, contract liabilities and certain information related to these balances as of and for the three and six months ended June 30, 2019 : As of June 30, 2019 As of January 1, 2019 (in thousands) Contract liabilities (1) $ 653 $ 1,622 __________ (1) Balance as of January 1, 2019 represents contract liabilities as adjusted for Topic 606. Three months ended Six months ended (in thousands) Revenue recognized in the period from: Amounts included in contract liability at the beginning of the period $ 1,069 $ 2,006 Remaining performance obligations As of June 30, 2019 , we had $65.5 million of remaining performance obligations, which includes deferred revenue and amounts that will be invoiced and recognized in future periods. The remaining performance obligations are limited only to arrangements that meet definition of a contract under Topic 606 as of June 30, 2019 . In addition to the practical expedient discussed above, we applied the practical expedient giving the optional exemption from disclosing the information about our remaining performance obligations for our service contracts for which the original contract duration is one year or less. The typical contract term is one year, although terms may vary by contract. We expect to recognize 52% of this balance over the next twelve months and the remainder within the following year. Costs to obtain a contract We capitalize incremental costs associated with obtaining customer contracts, specifically for sales commissions. These costs are deferred on our Condensed Consolidated Balance Sheets and amortized over the expected period of benefit on a straight-line basis. Based on the nature of our unique technology and services, the rate at which we continually enhance and update our technology, and our historical customer retention, the expected period of benefit is determined to be approximately five years. Amortization is within the sales and marketing line item on the accompanying Condensed Consolidated Statements of Operations and Comprehensive Loss. Deferred commissions are included in other assets on the accompanying Condensed Consolidated Balance Sheets. As of June 30, 2019 and January 1, 2019, our costs to obtain contracts were as follows: As of June 30, 2019 As of January 1, 2019 (in thousands) Deferred commissions (1) $ 6,514 $ 5,727 __________ (1) Balance as of January 1, 2019 represents deferred commissions as adjusted for Topic 606. During the three and six months ended June 30, 2019 , we recognized $0.6 million and $1.1 million of amortization related to deferred commission, respectively. These costs are recorded within the sales and marketing line item on the accompanying Condensed Consolidated Statements of Operations and Comprehensive Loss.

Investments and Fair Value Meas

Investments and Fair Value Measurements	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Investments and Fair Value Measurements	Investments and Fair Value Measurements Our total cash, cash equivalents and marketable securities consisted of the following: As of June 30, As of December 31, 2019 2018 (in thousands) Cash and cash equivalents: Cash $ 1,098 $ 32,546 Money market funds 212,365 2,419 U.S. Treasury securities — 1,998 Total cash and cash equivalents $ 213,463 $ 36,963 Marketable securities: Corporate notes and bonds $ 11,510 $ 12,852 Commercial paper 10,761 20,086 U.S. Treasury securities 2,994 5,932 Asset-backed securities 6,891 7,809 Total marketable securities $ 32,156 $ 46,679 Available-for-Sale Investments The following table summarizes adjusted cost, gross unrealized gains and losses, and fair value related to available-for-sale securities classified as marketable securities on the accompanying Condensed Consolidated Balance Sheets as of June 30, 2019 and December 31, 2018 : As of June 30, 2019 Amortized Gross Gross Fair (in thousands) Corporate notes and bonds $ 11,496 $ 14 $ — $ 11,510 Commercial paper 10,761 — — 10,761 U.S. Treasury securities 2,993 1 — 2,994 Asset-backed securities 6,888 3 — 6,891 Total available-for-sale investments $ 32,138 $ 18 $ — $ 32,156 As of December 31, 2018 Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Fair Value (in thousands) Corporate notes and bonds $ 12,867 $ — $ (15 ) $ 12,852 Commercial paper 20,086 — — 20,086 U.S. Treasury securities 5,933 — (1 ) 5,932 Asset-backed securities 7,817 — (8 ) 7,809 Total available-for-sale investments $ 46,703 $ — $ (24 ) $ 46,679 All securities classified as available-for-sale as of June 30, 2019 and December 31, 2018 have contractual maturities of one year or less. There were no securities in a continuous loss position for 12 months or longer as of June 30, 2019 and December 31, 2018 . Investments are reviewed periodically to identify possible other-than-temporary impairments. No impairment loss has been recorded on the securities included in the tables above, as we believe that the decrease in fair value of these securities is temporary and expects to recover at least up to the initial cost of investment for these securities. Fair Value of Financial Instruments For certain of our financial instruments, including cash held in banks, accounts receivable, and accounts payable, the carrying amounts approximate fair value due to their short maturities and are therefore excluded from the fair value tables below. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. There is a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: Level 1—Observable inputs such as quoted prices in active markets for identical assets or liabilities; Level 2—Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and Level 3—Unobservable inputs that are supported by little or no market activity, which require management judgment or estimation. We measure our cash equivalents, marketable securities, and convertible preferred stock warrant liabilities at fair value. We classify our cash equivalents and marketable securities within Level 1 or Level 2 because we value these investments using quoted market prices or alternative pricing sources and models utilizing market observable inputs. The fair value of our Level 1 financial assets is based on quoted market prices of the identical underlying security. The fair value of our Level 2 financial assets is based on inputs that are directly or indirectly observable in the market, including the readily available pricing sources for the identical underlying security that may not be actively traded. Prior to our IPO, we historically classified our convertible preferred stock warrant liabilities as Level 3. The convertible common stock warrant liabilities were valued using the Black-Scholes option-pricing model to determine the expected payout to calculate the fair value. Financial assets and liabilities measured and recorded at fair value on a recurring basis consisted of the following types of instruments: As of June 30, 2019 Level 1 Level 2 Level 3 Total (in thousands) Cash equivalents: Money market funds $ 212,365 $ — $ — $ 212,365 Total cash equivalents 212,365 — — 212,365 Marketable securities: Corporate notes and bonds — 11,510 — 11,510 Commercial paper — 10,761 — 10,761 U.S. Treasury securities — 2,994 — 2,994 Asset-backed securities — 6,891 — 6,891 Total marketable securities — 32,156 — 32,156 Total financial assets $ 212,365 $ 32,156 $ — $ 244,521 As of December 31, 2018 Level 1 Level 2 Level 3 Total (in thousands) Cash equivalents: Money market funds $ 2,419 $ — $ — $ 2,419 U.S. Treasury securities — 1,998 — 1,998 Total cash equivalents 2,419 1,998 — 4,417 Marketable securities: Corporate notes and bonds — 12,852 — 12,852 Commercial paper — 20,086 — 20,086 U.S. Treasury securities — 5,932 — 5,932 Asset-backed securities — 7,809 — 7,809 Total marketable securities — 46,679 — 46,679 Total financial assets $ 2,419 $ 48,677 $ — $ 51,096 Convertible preferred stock warrant liabilities $ — $ — $ 3,261 $ 3,261 Total financial liabilities $ — $ — $ 3,261 $ 3,261 The convertible preferred warrant liability is related to the warrants to purchase shares of preferred stock. The fair value of the warrant liability was determined based on significant inputs not observable in the market, which represents a Level 3 measurement within the fair value hierarchy. Upon the closing of the IPO, the warrant to purchase shares of preferred stock was converted into a warrant to purchase shares of our common stock. As a result, the warrant liability was remeasured a final time immediately prior to the IPO and reclassified to additional paid in capital within stockholders' equity. The following table sets forth a summary of the changes in the fair value of our Level 3 financial liabilities: 2019 (in thousands) Fair value, December 31, 2018 $ 3,261 Change in fair value of Level 3 financial liabilities 2,404 Conversion of convertible preferred stock warrants into Class B common stock warrants (5,665 ) Fair value, June 30, 2019 $ — The gains and losses from re-measurement of Level 3 financial liabilities are recorded as part of other expense, net in the accompanying Condensed Consolidated Statements of Operations and Comprehensive Loss. There were no transfers of assets and liabilities measured at fair value between Level 1 and Level 2, or between Level 2 and Level 3, during the three and six months ended June 30, 2019 and 2018 .

Balance Sheet Information

Balance Sheet Information	6 Months Ended
	Jun. 30, 2019
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Information	Balance Sheet Information Property and equipment, net Property and equipment, net consisted of the following: As of June 30, As of December 31, 2019 2018 (in thousands) Computer and networking equipment $ 83,236 $ 65,060 Leasehold improvements 3,268 3,259 Furniture and fixtures 559 539 Office equipment 535 513 Internal-use software 10,311 8,604 Property and equipment, gross 97,909 77,975 Accumulated depreciation and amortization (42,299 ) (35,621 ) Property and equipment, net $ 55,610 $ 42,354 Depreciation and amortization expense on property and equipment for the three months ended June 30, 2019 and 2018 was approximately $3.9 million and $3.3 million , respectively. Depreciation and amortization expense on property and equipment for six months ended June 30, 2019 and 2018 was approximately $7.6 million and $6.3 million , respectively. Included in these amounts was amortization expense for capitalized internal-use software costs of approximately $0.5 million and $0.4 million for the three months ended June 30, 2019 and 2018 , respectively and $1.0 million and $0.8 million for the six months ended June 30, 2019 and 2018 , respectively. As of June 30, 2019 and December 31, 2018 , the unamortized balance of capitalized internal-use software costs on our Condensed Consolidated Balance Sheets was approximately $6.0 million and $5.4 million , respectively. Accrued expenses Accrued expenses consisted of the following: As of June 30, As of December 31, 2019 2018 (in thousands) Accrued computer and networking equipment $ 7,752 $ — Accrued compensation and related benefits 5,495 3,952 Sales and use tax payable 3,273 3,077 Accrued colocation and bandwidth costs 2,499 3,049 Other accrued liabilities 6,082 5,457 Total accrued expenses $ 25,101 $ 15,535

Goodwill and Intangible Assets

Goodwill and Intangible Assets	6 Months Ended
	Jun. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets The changes in the carrying amount of goodwill for the six months ended June 30, 2019 are as follows: Six months ended (in thousands) Balance as of December 31, 2018 $ 360 Foreign currency translation (1 ) Balance as of June 30, 2019 $ 359 Intangible assets are comprised of internet protocol address costs and domain name costs that are subject to amortization. During the three and six months ended June 30, 2019 , we purchased additional internet protocol addresses and domain names for a gross carrying value of $0.6 million and $38.8 thousand , respectively. As of June 30, 2019 and December 31, 2018 , our intangible assets consisted of the following: As of June 30, 2019 As of December 31, 2018 Gross carrying value Accumulated amortization Net carrying value Gross carrying value Accumulated amortization Net carrying value (in thousands) Finite-lived intangible assets Internet protocol addresses $ 1,448 $ (289 ) $ 1,159 $ 852 $ (242 ) $ 610 Domain name 39 — 39 — — — Total finite-lived intangible assets $ 1,487 $ (289 ) $ 1,198 $ 852 $ (242 ) $ 610 The annual expected amortization expense of intangible assets subject to amortization as of June 30, 2019 is as follows: As of June 30, 2019 (in thousands) Remainder of 2019 $ 75 2020 158 2021 158 2022 155 2023 145 Thereafter 507 Total $ 1,198 We perform tests for impairment of goodwill and long-lived assets on an annual basis as of December 31 or more frequently if events or changes in circumstances indicate that the long-lived assets might be impaired. We did not record any impairment charges during the three and six months ended June 30, 2019 and 2018 . Aggregate expense related to amortization of intangible assets for the three months ended June 30, 2019 and 2018 was $26.3 thousand and $21.3 thousand , respectively. Aggregate expense related to amortization of intangible assets for the six months ended June 30, 2019 and 2018 was $47.6 thousand and $42.6 thousand , respectively.

Debt

Debt	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Debt Instruments	Debt Instruments Loan and Security Agreement In July 2013, we entered into a Loan and Security Agreement (the "Facility") with a bank related to an equipment facility providing us with an equipment line for advances of up to $2.5 million . The Facility was amended in September 2013 to increase the equipment line for advances up to $5.0 million (as amended, the "Prior Loan Agreement"), November 2014 to increase the equipment line for advances up to $15.0 million , and August 2016 to increase the equipment line for advances up to $17.5 million and allowed for reborrowing of amounts repaid under the equipment loan (as amended, the "Senior Loan Agreement"). The Senior Loan Agreement was additionally amended in February 2017 and March 2017, which extended the draw period to January 2018. In November 2017, we entered into a Second Amended and Restated Loan and Security Agreement, which amended the Senior Loan Agreement and increased the additional equipment line for advances up to an aggregate of $30.0 million through November 2018. As of June 30, 2019 and December 31, 2018 , $24.2 million and $29.2 million , respectively, has been drawn on this Second Amended and Restated Loan and Security Agreement. The interest rate associated with each advance under the Senior Loan Agreement is 1.75% above the floating prime rate (5.5% as of June 30, 2019). Beginning November 2018, we are obligated to make equal monthly payments of principal plus interest with repayment no later than November 1, 2021. Mezzanine Loan and Security Agreement In August 2016, we entered into a new Mezzanine Loan and Security Agreement ("Mezzanine Loan Agreement") with the bank and another third-party lender for advances of up to an aggregate of $12.5 million through June 2017. The minimum amount for each advance under the Mezzanine Loan Agreement was $2.5 million . Each advance under the Mezzanine Loan Agreement will accrue interest at a fixed per annum rate equal to 11.75% , payable monthly. All advances made under the Mezzanine Loan Agreement are due and payable in full on the maturity date of August 11, 2019. We have not received any advances under the Mezzanine Loan Agreement as of June 30, 2019. The Prior Loan Agreement, the Senior Loan Agreement, and the Mezzanine Loan Agreement are secured by a security interest on substantially all of our assets, including the equipment purchased with the advances. The Prior Loan Agreement, the Senior Loan Agreement, and the Mezzanine Loan Agreement also contain customary events of default including, among other things, that during the existence of an event of default, interest on the obligations could be increased by 5% . We are required to comply with certain affirmative and negative covenants in the Senior Loan Agreement, including a requirement that we maintain a ratio of cash and cash equivalents plus net unbilled accounts receivable to current liabilities plus long-term debt minus the current portion of any deferred revenue (an Adjusted Quick Ratio) at all times of at least 1.15 to 1.0 as well as a requirement that we achieve trailing three-month revenues evaluated on a monthly basis in amounts not less than 80% of our board approved annual budget. We are also required to maintain at least $10.0 million in unrestricted cash with the lenders or their affiliates at all times. Capital Lease Agreement In June 2017, we entered into a Capital Lease Agreement with an equipment provider for $5.0 million in network equipment, at an annual interest rate of 5.24% over a term of four years. In March 2018, we entered into an additional agreement with the equipment provider for $0.5 million in network equipment at an annual interest rate of 5.38% over a term of four years. In February 2019 and March 2019, we entered into additional agreements with the equipment provider for $2.9 million and $1.3 million , respectively, in network equipment, at an annual interest rate of 5.38% over terms of three years. The additional agreements incorporate the same terms and conditions as those under the Capital Lease Agreement entered into in June 2017. As of June 30, 2019 and December 31, 2018 , $6.6 million and $3.5 million was outstanding under the Capital Lease Agreement. The agreement provides for a bargain purchase price at the end of the term. The amortization of leased assets is included in depreciation and amortization expense. Credit Facility In December 2018, we entered into a Second Lien Credit Agreement under which were permitted to borrow up to $30.0 million ("Credit Facility"). As part of this agreement, the Second Amendment to Amended and Restated Loan was amended to allow for this additional indebtedness. The advances under the Credit Facility bear interest at a rate of prime plus 4.25% . We are obligated to make repayment of interest only until December 2021 at which time all outstanding principal is due. As of June 30, 2019 and December 31, 2018 , $20.0 million has been drawn on this Credit Facility. All outstanding loans under the Credit Facility, if not paid earlier, will become due and payable on December 24, 2021. We are required to comply with certain affirmative and negative covenants in the Second Lien Credit Agreement, including a requirement that we achieve trailing three-month revenues evaluated on a monthly basis in amounts not less than 75% of its board approved annual budget. As of June 30, 2019 and December 31, 2018 , we are in compliance with all of our covenants described in the preceding paragraphs. The following table reflects the carrying values of the debt agreements as of June 30, 2019 and December 31, 2018 : As of June 30, As of December 31, 2019 2018 (in thousands) Liability component: Principal amount—Second Amendment to Amended and Restated Loan and Security Agreement $ 44,167 $ 49,167 Less: unamortized debt issuance costs (68 ) (1,896 ) Less: current portion of long-term debt (30,000 ) (10,000 ) Long-term debt, less current portion—Second Amendment to Amended and Restated Loan and Security Agreement $ 14,099 $ 37,271 Principal amount—Capital Lease Agreement 6,601 3,538 Less: current portion of long-term debt (2,822 ) (1,370 ) Long-term debt, less current portion—Capital Lease Agreement $ 3,779 $ 2,168 Total long-term debt, less current portion $ 17,878 $ 39,439 Contractual future repayments for the above as of June 30, 2019 are as follows: Principal Interest Total (in thousands) Remainder of 2019 $ 26,393 $ 1,178 $ 27,571 2020 12,899 1,290 14,189 2021 11,404 404 11,808 2022 72 1 73 Total $ 50,768 $ 2,873 $ 53,641 Interest expense related to debt for the three months ended June 30, 2019 and 2018 was $3.0 million and $0.4 million , respectively. Interest expense related to debt for the six months ended June 30, 2019 and 2018 was $4.2 million and $0.7 million , respectively.

Common Stock Warrant Liabilitie

Common Stock Warrant Liabilities	6 Months Ended
	Jun. 30, 2019
Warrants and Rights Note Disclosure [Abstract]
Common Stock Warrant Liabilities	Common Stock Warrant Liabilities We issued convertible preferred stock warrants in connection with debt agreements entered into on various dates as described in Note 7, "Debt" . Immediately upon closing of the IPO, our warrants to purchase convertible preferred stock were automatically converted to warrants to purchase an equal number of shares of our Class B common stock. As a result, the warrant liability was remeasured a final time immediately prior to the IPO and reclassified to additional paid in capital within stockholders' equity. Changes in the fair value are recorded within other expense, net on the accompanying Condensed Consolidated Statements of Operations and Comprehensive Loss. The fair value of the warrants as of May 17, 2019 was estimated using the following assumptions: Series B Series C Series D Series F Total Fair value (in thousands) $ 1,818 $ 792 $ 668 $ 2,387 $ 5,665 Expected remaining term (in years) 4.46 5.47 7.21 9.62 Risk-free interest rate 2.17 % 2.20 % 2.27 % 2.37 % Expected volatility 39.0 % 39.3 % 40.2 % 42.4 % Dividend yield — — — — The fair value of the warrants as of December 31, 2018 was estimated using the following assumptions: Series B Series C Series D Series F Total Fair value (in thousands) $ 857 $ 407 $ 358 $ 1,639 $ 3,261 Expected remaining term (in years) 4.84 5.84 7.59 10.00 Risk-free interest rate 2.62 % 2.62 % 2.62 % 2.80 % Expected volatility 50.0 % 50.0 % 50.0 % 50.0 % Dividend yield — — — — In the three and six months ended June 30, 2019 , the Class B common stock warrants related to the Facility, the Class B common stock warrants related to the Prior Loan Agreement, the Class B common stock warrants related to a previously outstanding term loan agreement and the Class B common stock warrants related to the Mezzanine Loan Agreement were exercised under the cashless exercise method pursuant to the corresponding warrant agreements. As a result of such exercises, we issued 172,380 shares of our Class B common stock. As of June 30, 2019 , the outstanding warrants are classified and recorded as additional paid-in capital on the Condensed Consolidated Balance Sheets. As of December 31, 2018

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Operating Lease Commitments We lease our facilities under non-cancelable operating leases. These operating leases expire at various dates through January 2021 and generally require the payment of real estate taxes, insurance, maintenance, and operating costs. The lease agreements generally provide for rental payments on a graduated basis and for options to renew, which could increase future minimum lease payments if exercised. There have been no material changes in these long-term commitments, as compared to those described in the Prospectus. We recognize rent expense on a straight-line basis over the lease period and have accrued for rent expense incurred but not paid. Rent expense for the three months ended June 30, 2019 and 2018 was $1.8 million and $1.7 million , respectively. Rent expense for the six months ended June 30, 2019 and 2018 was $3.5 million and $3.5 million , respectively. During the three and six months ended June 30, 2019 and 2018 , we had sublease agreements with tenants of various properties vacated by us. The amount paid to us by these sublease tenants was approximately $0.3 million and $0.2 million during the three months ended June 30, 2019 and 2018 , respectively. The amount paid to us by these sublease tenants was approximately $0.6 million and $0.5 million during the six months ended June 30, 2019 and 2018 , respectively. Purchase Commitments As of June 30, 2019 , we had long-term commitments for cost of revenue related agreements (i.e., bandwidth usage, colocation, peering and other managed services with various networks, internet service providers ("ISPs") and other third-party vendors), and various non-cancelable software as a service ("SaaS") agreements. Additionally, as of June 30, 2019 , we had entered into purchase orders with various vendors. There have been no material changes to our purchase commitments related to SaaS agreements as compared to those described in the Prospectus. The minimum future commitments related to cost of revenue related agreements as of June 30, 2019 were as follows. Cost of Revenue Commitments (in thousands) Remainder of 2019 $ 33,104 2020 17,591 2021 4,796 2022 968 Total $ 56,459 Legal Matters We are party to various disputes that management considers routine and incidental to its business. Management does not expect the results of any of these routine actions to have a material effect on our business, results of operations, financial condition, or cash flows. Indemnification We enter into standard indemnification agreements in the ordinary course of business. Pursuant to these agreements, we agree to indemnify, hold harmless, and reimburse the indemnified party for losses suffered or incurred by the indemnified party, generally our business partners or customers, in connection with our provision of its services. Generally, these obligations are limited to claims relating to infringement of a patent, copyright, or other intellectual property right, breach of the Company’s security or data protection obligations, or the Company’s negligence, willful misconduct, or violation of law. Subject to applicable statutes of limitation, the term of these indemnification agreements is generally for the duration of the agreement. The maximum potential amount of future payments we could be required to make under these indemnification agreements is unlimited; however, we carry insurance that covers certain third-party claims relating to our services and could limit our exposure in that respect. We have agreed to indemnify each of our officers and directors during his or her lifetime for certain events or occurrences that happen by reason of the fact that the officer or director is, was, or has agreed to serve as an officer or director of the Company. We have director and officer insurance policies that may limit our exposure and may enable us to recover a portion of certain future amounts paid. To date, we have not encountered material costs as a result of such indemnification obligations and have not accrued any related liabilities in our financial statements. In assessing whether to establish an accrual, we consider such factors as the degree of probability of an unfavorable outcome and the ability to make a reasonable estimate of the amount of loss.

Convertible Preferred Stock

Convertible Preferred Stock	6 Months Ended
	Jun. 30, 2019
Temporary Equity Disclosure [Abstract]
Convertible Preferred Stock	Convertible Preferred Stock As of December 31, 2018 , we had seven outstanding series of Preferred Stock ("Series Preferred") each with a par value of $0.00002 per share, which were convertible at the option of the holder. The Series Preferred was classified as temporary equity on the accompanying Condensed Consolidated Balance Sheets as of December 31, 2018 . Immediately upon closing of the IPO, our convertible preferred stock was automatically converted to shares of our Class B common stock. We had no convertible preferred stock issued or outstanding as of June 30, 2019 . A summary of the Preferred Stock outstanding as of December 31, 2018 and other related information is as follows: As of December 31, 2018 Shares Authorized Shares Issued and Outstanding Net Carrying Amount Liquidation Preference (in thousands except share data) Series Seed Preferred Stock 8,049,365 8,049,364 $ 1,200 $ 1,200 Series A Preferred Stock 2,733,520 2,733,518 1,050 1,050 Series B Preferred Stock 11,058,835 10,945,209 11,260 11,260 Series C Preferred Stock 9,805,905 9,753,060 41,420 41,527 Series D Preferred Stock 11,675,463 11,627,903 74,912 75,000 Series E Preferred Stock 6,609,032 6,609,030 49,863 50,000 Series F Preferred Stock 4,216,523 3,912,129 39,879 40,000 Total 54,148,643 53,630,213 $ 219,584 $ 220,037

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2019
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders' Equity Common Stock Our Amended and Restated Certificate of Incorporation, as amended and restated in May 2019, authorizes the issuance of 1,000,000,000 shares of Class A common stock and 94,129,050 shares of Class B common stock, each at a par value per share of $0.00002 . Holders of Class A common stock are entitled to one vote per share and holders of Class B common stock are entitled to 10 votes per share. As of June 30, 2019 and December 31, 2018 , 80,433,917 and 25,026,001 shares of Class B common stock were issued and outstanding, respectively. As of June 30, 2019 , 12,995,158 shares of Class A common stock were issued and outstanding. Preferred Stock Our Amended and Restated Certificate of Incorporation, as amended and restated in May 2019, authorizes the issuance of 10,000,000 shares of Preferred Stock, at a par value per share of $0.00002 , with rights and preferences, including voting rights, designated from time to time by the Board of Directors (the "Board"). Equity Incentive Plans In March 2011, our stockholders approved the Fastly, Inc. 2011 Equity Incentive Plan ("2011 Plan"). The 2011 Plan was amended in February 2013, May 2014, July 2015, December 2016, April 2017, and June 2018. The 2011 Plan allows for the issuance of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, and restricted stock unit awards to employees, directors, and, consultants of the Company. There were 23,578,923 shares of common stock reserved for issuance under the 2011 Plan as of June 30, 2019 . There were 21,689,410 shares of common stock reserved for issuance under the 2011 Plan as of December 31, 2018 . Options granted under the 2011 Plan generally expire within 10 years from the date of grant and generally vest over four years , at the rate of 25% on the first anniversary of the date of grant and ratably on a monthly basis over the remaining 36-month period thereafter based on continued service and are exercisable for shares of our Common Stock. As of June 30, 2019 , there were no shares of common stock available for issuance pursuant to future grants under the 2011 Plan. As of December 31, 2018 , there were 609,804 shares of common stock available for issuance pursuant to future grants under the 2011 Plan. In May 2019, the Board adopted our 2019 Equity Incentive Plan (the "2019 Plan"), and our stockholders approved the 2019 Plan. The 2019 Plan allows for the issuance of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock units awards, performance-based stock awards, and other forms of equity compensation, which are collectively referred to as stock awards. Additionally, the 2019 Plan provides for the grant of performance cash awards. Incentive stock options may be granted only to employees. All other awards may be granted to employees, including officers, and to non-employee directors and consultants. Options granted under the 2019 Plan generally expire within 10 years from the date of grant and generally vest over four years , at the rate of 25% on the first anniversary of the date of grant and ratably on a monthly basis over the remaining 36 -month period thereafter based on continued service and are exercisable for shares of our Common Stock. There were 14,400,000 shares of Common Stock reserved and available for issuance under the 2019 Plan as of June 30, 2019 . No further shares will be issued under the 2011 Plan following the effectiveness of the 2019 Plan. In May 2019, the Board approved the Employee Stock Purchase Plan ("ESPP"), which was approved by our stockholders in May 2019. The ESPP allows eligible employees to purchase shares of our common stock through payroll deductions of up to 15% of their eligible compensation, subject to a maximum of $25,000 per calendar year. Shares reserved for issuance under the ESPP include 2,500,000 shares of common stock. The ESPP provides for six - month offering periods, commencing in May and November of each year. At the end of each offering period employees are able to purchase shares at 85% of the lower of the fair market value of our common stock on the first trading day of the offering period or on the last day of the offering period. Stock Option Activity The following table summarizes stock option activity during the six months ended June 30, 2019 : Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term Aggregate Intrinsic Value (in thousands) (in years) (in thousands) Outstanding at December 31, 2018 12,210 $ 2.96 7.80 $ 64,590 Granted 2,119 9.19 Exercised (1,418 ) 2.15 Cancelled/forfeited (568 ) 4.52 Outstanding at June 30, 2019 12,343 $ 4.04 7.72 $ 200,448 Vested and exercisable at June 30, 2019 7,305 $ 2.34 6.73 $ 131,052 The total pre-tax intrinsic value of options exercised during the six months ended June 30, 2019 and 2018 was $10.9 million and $1.1 million , respectively. The total grant date fair value of employee options vested for the six months ended June 30, 2019 and 2018 was $2.8 million and $1.7 million , respectively. The weighted average grant-date fair value for options granted to employees during the six months ended June 30, 2019 and 2018 was $5.36 and $1.95 , respectively. Early Exercise of Stock Options Certain stock options granted by the Company are exercisable at the date of grant, with unvested shares subject to repurchase by the Company in the event of voluntary or involuntary termination of employment of the stockholder. Such exercises are recorded as a liability on the accompanying Condensed Consolidated Balance Sheets and reclassified into equity as the options vest. As of June 30, 2019 and December 31, 2018 , a total of 280,942 and 244,658 shares of Common Stock were subject to repurchase by the Company at the lower of (i) the fair market value of such shares on the date of repurchase, or (ii) the original exercise price of such shares. The corresponding exercise value of approximately $1.2 million and $1.0 million as of June 30, 2019 and December 31, 2018 , respectively, is recorded in other current liabilities and other liabilities on the accompanying Condensed Consolidated Balance Sheets. The activity of non-vested shares as a result of early exercise of options granted to employees and non-employees, is as follows: Six months ended June 30, 2019 2018 (in thousands) Beginning balance 245 138 Early exercise of options 117 — Vested (81 ) (48 ) Repurchased — (11 ) Ending balance 281 79 Employee Stock Options We estimate the fair value of stock options on the date of grant using the Black-Scholes option-pricing model. Each of the Black-Scholes inputs is subjective and generally requires significant judgments to determine. We estimated the fair value of stock option awards during the six months ended June 30, 2019 and 2018 on the date of the grant using the Black-Scholes option pricing model with the following weighted-average assumptions: Six months ended June 30, 2019 2018 Fair value of common stock $ 11.14 $ 4.05 Expected term (in years) 6.02 6.09 Risk-free interest rate 2.45 % 2.76 % Expected volatility 39.6 % 41.3 % Dividend yield — % — % During the three months ended June 30, 2019 and 2018 , we recorded stock-based compensation expense from stock options of approximately $1.9 million and $1.0 million , respectively. During the six months ended June 30, 2019 and 2018 , we recorded stock-based compensation expense from stock options of approximately $3.3 million and $1.8 million , respectively. As of June 30, 2019 , total unrecognized stock-based compensation cost related to outstanding unvested stock options that are expected to vest was $19.6 million . This unrecognized stock-based compensation cost is expected to be recognized over a weighted-average period of approximately 3.1 years. ESPP The ESPP allows eligible employees to purchase shares of our common stock through payroll deductions of up to 15% of their eligible compensation. The ESPP provides for six-month offering periods, commencing in May and November of each year. We estimate the fair value of shares to be issued under the ESPP on the first day of the offering period using the Black-Scholes valuation model. The inputs to the Black-Scholes option pricing model are our stock price on the first date of the offering period, the risk-free interest rate, the estimated volatility of our stock price over the term of the offering period, the expected term of the offering period and the expected dividend rate. Stock-based compensation expense related to the ESPP is recognized on a straight-line basis over the offering period. Forfeitures are recognized as they occur. We estimated the fair value of shares granted under the ESPP on the first date of the offering period using the Black-Scholes option pricing model with the following assumptions: Six months ended June 30, 2019 2018 Fair value of common stock $ 6.92 N/A Expected term (in years) 0.50 N/A Risk-free interest rate 2.35 % N/A Expected volatility 36.4 % N/A Dividend yield — % N/A During the six months ended June 30, 2019 , we withheld $0.8 million in contributions from employees and recognized $0.4 million in stock-based compensation expense related to the ESPP. No contributions were withheld, and no stock-based compensation expense was recognized related to the ESPP in the three and six months ended June 30, 2018 . No common stock was issued under the ESPP in the three and six months ended June 30, 2018 and 2019 . Stock-based Compensation Expense The following table summarizes the components of total stock-based compensation expense included in the accompanying Condensed Consolidated Statements of Operations and Comprehensive Loss: Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 (in thousands) Stock-based compensation expense by caption: Cost of revenue $ 293 $ 71 $ 437 $ 123 Research and development 714 324 1,146 600 Sales and marketing 596 226 965 451 General and administrative 640 369 1,162 664 Total $ 2,243 $ 990 $ 3,710 $ 1,838

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stockholders	Net Loss Per Share Attributable to Common Stockholders We compute net loss per share using the two-class method required for multiple classes of common stock and participating securities. The rights of the holders of the Class A common stock and Class B common stock are identical, except with respect to voting and conversion. Accordingly, the Class A common stock and Class B common stock share equally in our net losses. Prior to the IPO, our participating securities also included convertible preferred stock. The holders of convertible preferred stock did not have a contractual obligation to share in our losses, and as a result net losses were not allocated to these participating securities. The following table sets forth the calculation of basic and diluted net loss per share attributable to common stockholders during the periods presented. The shares issued in the IPO, the shares issued pursuant to the exercise by the underwriters of an option to purchase additional shares, and the shares of Class A and Class B common stock issued upon conversion of the outstanding shares of convertible preferred stock in the IPO are included in the table below weighted for the period outstanding: Three months ended June 30, 2019 2018 Class A Class B Class A (1) Class B (2) (in thousands, except per share amounts) Net loss $ (1,685 ) $ (13,902 ) N/A $ (5,836 ) Net loss attributable to common stockholders $ (1,685 ) $ (13,902 ) N/A $ (5,836 ) Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted 6,464 53,317 N/A 24,127 Net loss per share attributable to common stockholders, basic and diluted $ (0.26 ) $ (0.26 ) N/A $ (0.24 ) Six months ended June 30, 2019 2018 Class A Class B Class A (1) Class B (2) (in thousands, except per share amounts) Net loss $ (1,931 ) $ (23,383 ) N/A $ (15,142 ) Net loss attributable to common stockholders $ (1,931 ) $ (23,383 ) N/A $ (15,142 ) Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted 3,250 39,349 N/A 24,034 Net loss per share attributable to common stockholders, basic and diluted $ (0.59 ) $ (0.59 ) N/A $ (0.63 ) __________ (1) Class A common stock includes the issuance of 12.9 million shares of Class A common stock issued by us in connection with our IPO and shares issued upon the exercise of options subsequent to our IPO. (2) Class B common stock includes, for all periods presented, the conversion of all of our preferred stock into an aggregate of 53.6 million shares of our Class B common stock upon closing of the IPO. Since we were in a loss position for the periods presented, basic net loss per share is the same as diluted net loss per share as the inclusion of all potential common shares outstanding would have been anti-dilutive. The potential shares of common stock that were excluded from the computation of diluted net loss per share attributable to common stockholders for the period presented because including them would have been antidilutive are as follows: Number of Shares As of June 30, 2019 2018 (in thousands) Convertible preferred stock — 53,550 Stock options 12,343 10,928 Early exercised stock options 281 79 Convertible common stock warrants 259 — Convertible preferred stock warrants — 214 Shares issuable pursuant to the ESPP 60 — Total 12,943 64,771

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Our provision for income taxes for interim periods is determined using an estimate of our annual effective tax rate, adjusted for discrete items, if any, that arise during the period. Each quarter, we update our estimate of the annual effective tax rate, and if the estimated annual effective tax rate changes, we make a cumulative adjustment in such period. In the three months ended June 30, 2019 and 2018 , we recorded an income tax provision of $82.0 thousand and $35.0 thousand , respectively. In the six months ended June 30, 2019 and 2018 , we recorded an income tax provision of $137.0 thousand and $93.0 thousand , respectively. We continue to maintain a valuation allowance for our U.S. Federal and state net deferred tax assets. The tax expense for the three and six months ended June 30, 2019 and 2018 was primarily due to foreign and state income tax expense.

Information About Revenue and G

Information About Revenue and Geographic Areas	6 Months Ended
	Jun. 30, 2019
Segment Reporting [Abstract]
Information About Revenue and Geographic Areas	Information About Revenue and Geographic Areas We consider operating segments to be components of the Company in which separate financial information is available and is evaluated regularly by our Chief Operating Decision Maker ("CODM") in deciding how to allocate resources and in assessing performance. Our CODM is the Chief Executive Officer ("CEO"). The CEO reviews financial information presented on a consolidated basis, accompanied by information about revenue customer size and industry vertical for purposes of allocating resources and evaluating financial performance. We have determined that we operate under one business activity with no segment managers who are held accountable for operations, operating results, or plans for levels or components below the consolidated unit level. Accordingly, we have determined that we have a single reporting segment and operating unit structure. Revenue Revenue by geography is based on the billing address of the customer. Refer to Note 3, "Revenue" for more information on net revenue by geographic region. Long-Lived Assets The following table presents long-lived assets by geographic region: As of June 30, As of December 31, 2019 2018 (in thousands) United States $ 36,723 $ 28,723 All other countries 18,887 13,631 Total long-lived assets $ 55,610 $ 42,354

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2019
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions In July 2016, a stockholder borrowed approximately $0.1 million to exercise stock options for 53,125 shares of common stock pursuant to a promissory note from the stockholder. The note bears interest at a rate of 1.77% . In June 2019, the promissory note was repaid in full. Prior to repayment, for the purposes of the financial statements, the shares were not reported as exercised, issued, or outstanding. This stockholder is not one of our executive officers or directors. Approximately $75,000 was outstanding as of December 31, 2018 . There was no outstanding balance as of June 30, 2019 .

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2019
Subsequent Events [Abstract]
Subsequent Event	Subsequent Event In December 2018, we entered into a $30.0 million Credit Facility. As of June 30, 2019, $20.0 million had been drawn on this Credit Facility and was included in the current portion of long-term debt line item on the accompanying Condensed Consolidated Balance Sheets. On July 8, 2019, the $20.0 million outstanding loan, which was due and payable on December 24, 2021, was paid in full, in accordance with the terms of the Credit Facility. Upon payment, the Credit Facility was closed. Refer to Note 7, "Debt" , for further details on the Credit Facility.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The interim unaudited condensed consolidated financial statements and accompanying notes have been prepared in accordance with United States generally accepted accounting principles ("U.S. GAAP") along with instructions to Form 10-Q and Article 10 of Securities and Exchange Commission ("SEC") Regulation S-X.
Principles of Consolidation and Unaudited Interim Financial Statements	Principles of Consolidation The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. Unaudited Interim Financial Statements The accompanying interim condensed consolidated balance sheet as of June 30, 2019 , the related interim condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2019 and 2018 , the condensed consolidated statements of cash flows, the condensed consolidated statements of convertible preferred stock and stockholders' equity (deficit) for the six months ended June 30, 2019 and 2018 , and the related footnote disclosures are unaudited. The unaudited interim condensed consolidated financial statements have been prepared in accordance with U.S. GAAP. In management’s opinion, the unaudited financial statements have been prepared on the same basis as the audited financial statements and include all adjustments, which include only normal recurring adjustments necessary for the fair presentation of our financial position as of June 30, 2019 , our results of operations and comprehensive income for the three and six months ended June 30, 2019 and 2018 , and our statements of cash flows for the six months ended June 30, 2019 and 2018 . The results for the three and six months ended June 30, 2019 are not necessarily indicative of the results expected for the full fiscal year or any other periods.
Use of Estimates	Use of Estimates The preparation of our condensed consolidated financial statements requires us to make estimates, judgments, and assumptions that affect the reported amounts of assets, liabilities, revenue, costs and expenses, and related disclosures. Actual results and outcomes could differ significantly from our estimates, judgments, and assumptions. Significant estimates, judgments, and assumptions used in these financial statements include, but are not limited to, those related to revenue, accounts receivable and related reserves, useful lives and realizability of long-lived assets, income tax reserves, and accounting for stock-based compensation. Estimates are periodically reviewed in light of changes in circumstances, facts, and experience. The effects of material revisions in estimates are reflected in the condensed consolidated financial statements in the period of change and prospectively from the date of the change in estimate.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject us to significant concentration of credit risk consist primarily of cash, cash equivalents, marketable securities, and accounts receivable. The primary focus of our investment strategy is to preserve capital and meet liquidity requirements. Our investment policy addresses the level of credit exposure by limiting the concentration in any one corporate issuer or sector and establishing a minimum allowable credit rating. To manage the risk exposure, we invest cash equivalents and marketable securities in a variety of fixed income securities, including government and investment-grade debt securities, and money market funds. We place our cash primarily in checking and money market accounts with reputable financial institutions. Deposits held with these financial institutions may exceed the amount of insurance provided on such deposits, if any. Concentrations of credit risk with respect to accounts receivable are primarily limited to certain customers to which we make substantial sales. Our customer base consists of a large number of geographically dispersed customers diversified across several industries. To reduce risk, we routinely assess the financial strength of our customers. Based on such assessments, we believe that our accounts receivable credit risk exposure is limited. No customer accounted for more than 10% of revenue for the three and six months ended June 30, 2019 and 2018 or more than 10% of the total accounts receivable balance as of June 30, 2019 and December 31, 2018 .
Recently Adopted and Issued Accounting Pronouncements	Recently Adopted Accounting Pronouncements In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASU 2014-09"), which amends the existing accounting standards for revenue recognition, Topic 605, and outlines a single set of comprehensive principles for recognizing revenue under U.S. GAAP. Among other things ASU 2014-09 requires entities to assess the products or services promised in contracts with customers at contract inception to determine the appropriate unit at which to record revenue, which is referred to as a performance obligation. Revenue is recognized when or as control of the promised products or services is transferred to customers at an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those products or services. We have adopted ASU 2014-09 as of January 1, 2019 using the modified retrospective method applied to those contracts which were not completed as of January 1, 2019. Revenues and contract assets or liabilities for contracts completed prior to January 1, 2019 are presented under Topic 605, and revenues and contract assets and liabilities from contracts which were not completed or started after December 31, 2018 are presented under Topic 606. We recorded a net increase in stockholders’ equity (retained earnings) of $5.7 million as of January 1, 2019 due to the cumulative impact of adopting Topic 606 and Topic 340, Other Assets and Deferred Costs. Refer to Note 3, "Revenue" , in the Notes to the Condensed Consolidated Financial Statements for further information. In August 2016, FASB issued Accounting Standards Update No. 2016-15, Statement of Cash Flows (Topic 230) Classification of Certain Cash Receipts and Cash Payments ("ASU 2016-15"), which clarifies how entities should classify cash receipts and cash payments related to eight specific cash flow matters on the statement of cash flows, with the objective of reducing existing diversity in practice. ASU 2016-15 designates the appropriate class flow classification, including requirements to allocate certain components of these cash receipts and payments among operating, investing, and financing activities. The guidance is effective for financial statements issued for fiscal years beginning after December 15, 2018. We adopted this guidance effective January 1, 2019 using the retrospective transition approach for all periods presented. The adoption of ASU 2016-15 did not have a material impact on our condensed consolidated financial statements. In November 2016, the FASB issued Accounting Standards Update No. 2016-18, Statement of Cash Flows (Topic 230) ("ASU 2016-18"), which requires companies to include amounts generally described as restricted cash and restricted cash equivalents in cash and cash equivalents when reconciling beginning-of-period and end-of-period total amounts shown on the statement of cash flows. We adopted this guidance effective January 1, 2019, using the retrospective transition approach for all periods presented. The adoption of ASU 2016-18 did not have a material impact on our condensed consolidated financial statements. In January 2017, the FASB issued Accounting Standards Update No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business ("ASU 2017-01"), which changes the definition of a business to assist entities with evaluating whether transactions should be accounted for as transfers of assets or business combinations. The guidance is effective for financial statements issued for fiscal years beginning after December 15, 2018. We adopted this guidance effective January 1, 2019, using the prospective approach. The adoption of ASU 2017-01 did not have a material impact on our condensed consolidated financial statements. In January 2017, the FASB issued Accounting Standards Update No. 2017-04 , Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment ("ASU 2017-04"), which eliminates step two from the goodwill impairment test. Under this guidance, an entity should recognize an impairment charge for the amount by which the carrying amount of a reporting unit exceeds its fair value up to the amount of goodwill allocated to that reporting unit. The guidance is effective for financial statements issued for fiscal years beginning after December 15, 2020, although early adoption is permitted for annual and interim goodwill impairment testing dates following January 1, 2017. We have elected to early adopt this guidance beginning in the second quarter of 2019 using the prospective method. The adoption of ASU 2017-04 did not have a material impact on our condensed consolidated financial statements. In June 2018, the FASB issued Accounting Standards Update No. 2018-07, Improvements to Nonemployee Share-Based Payment Accounting ("ASU 2018-07"), which simplifies the accounting for share-based payments granted to nonemployees for goods and services. Under ASU 2018-07, certain guidance such as payments to nonemployees would be aligned with the requirements for share-based payments granted to employees. The guidance is effective for fiscal years beginning after December 15, 2019, and interim periods within that fiscal year, although early adoption is permitted. We have elected to early adopt the guidance beginning January 1, 2019. The adoption of ASU 2018-07 did not have a material impact on our condensed consolidated financial statements. Recently Issued Accounting Standards We qualify as an "emerging growth company" as defined in the Jumpstart Our Business Startups Act of 2012 ("JOBS Act") and therefore have elected to continue to take advantage of certain exemptions from various public company reporting requirements, including delaying adoption of new or revised accounting standards until those standards apply to private companies. We have elected to use this extended transition period under the JOBS Act. The effective dates shown below reflect the election to use the extended transition period. In February 2016, the FASB issued new guidance, Accounting Standard Update No. 2016-02, Leases (Topic 842) ("ASU 2016-02"), which establishes the principles to report transparent and economically neutral information about the assets and liabilities that arise from leases. Accordingly, this new standard introduces a lessee model that brings most operating leases on the balance sheet and also aligns certain of the underlying principles of the new lessor model with those in the new revenue recognition standard. The guidance is effective for financial statements issued for fiscal years beginning after December 15, 2019 using the modified retrospective method, although the optional transition method can also be applied. We are currently evaluating the appropriate transition method and impact of this guidance on our condensed consolidated financial statements and related disclosures.
Revenue recognition	Revenue recognition Revenue is recognized upon transfer of control of promised products or services to customers in an amount that reflects the consideration we expect to receive in exchange for those products or services. We enter into contracts that can include various combinations of products and services, each of which are distinct and accounted for as separate performance obligations. Revenue is recognized net of any taxes collected from customers, which are subsequently remitted to governmental authorities. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in Topic 606. Our contracts with customers often include promises to transfer multiple products and services to a customer. Determining whether products and services are considered distinct performance obligations that should be accounted for separately versus together may require significant judgment. For contracts with multiple performance obligations, we allocate the contract transaction price to each performance obligation using our estimate of the standalone selling price ("SSP") of each distinct good or service in the contract. Judgment is required to determine the SSP for each distinct performance obligation. We analyze separate sales of our products and services as a basis for estimating the SSP of our products and services. We then use that SSP as the basis for allocating the transaction price when our product and services are sold together in a contract with multiple performance obligations. In instances where SSP is not directly observable, such as when we do not sell the product or service separately, we determine the SSP using information that may include market conditions and other observable inputs. We typically have more than one SSP for individual products and services due to the stratification of those products and services by customers and circumstances. In these instances, we may use information such geographic region and distribution channel in determining the SSP. The transaction price in a contract is typically equal to the minimum commit price in the contract less any discounts provided. Because our typical contracts represent distinct services delivered over time with the same pattern of transfer to the customer, usage-based consideration primarily related to actual consumption over the minimum commit levels is allocated to the period to which it relates. The amount of consideration recognized for usage above the minimum commit price is limited to the amount we expect to be entitled to receive in exchange for providing services. We have elected to apply the practical expedient for estimating and disclosing the variable consideration when variable consideration is allocated entirely to a wholly unsatisfied performance obligation or to a wholly unsatisfied promise to transfer a distinct good or service that forms part of a single performance obligation from our remaining performance obligations under these contracts. Performance obligations represent stand-ready obligations that are satisfied over time as the customer simultaneously receives and consumes the benefits provided by us. These obligations can be content delivery, security, professional services, support, edge cloud platform services, and others. Accordingly, our revenue is recognized over time, consistent with the pattern of benefit provided to the customer over the term of the agreement. At times, customers may request changes that either amend, replace, or cancel existing contracts. Judgment is required to determine whether the specific facts and circumstances within the contracts should be accounted for as a separate contract or as a modification. In contracts where there are timing differences between when we transfer a promised good or service to the customer and when the customer pays for that good or service, we have determined our contracts do not include a significant financing component. We have also elected the practical expedient to not measure financing components for any contract where the timing difference is less than one year. From time to time we enter into arrangements to establish and run private POPs for customers. These arrangements include content delivery services as well as professional services and the provision of hardware. For accounting purposes, we have determined that the provisioning of hardware is an operating lease. We recognize the revenue from these leases monthly on a straight-line basis over the term of the relevant customer agreements.
Fair value of financial instruments	Fair Value of Financial Instruments For certain of our financial instruments, including cash held in banks, accounts receivable, and accounts payable, the carrying amounts approximate fair value due to their short maturities and are therefore excluded from the fair value tables below. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. There is a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: Level 1—Observable inputs such as quoted prices in active markets for identical assets or liabilities; Level 2—Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and Level 3—Unobservable inputs that are supported by little or no market activity, which require management judgment or estimation. We measure our cash equivalents, marketable securities, and convertible preferred stock warrant liabilities at fair value. We classify our cash equivalents and marketable securities within Level 1 or Level 2 because we value these investments using quoted market prices or alternative pricing sources and models utilizing market observable inputs. The fair value of our Level 1 financial assets is based on quoted market prices of the identical underlying security. The fair value of our Level 2 financial assets is based on inputs that are directly or indirectly observable in the market, including the readily available pricing sources for the identical underlying security that may not be actively traded. Prior to our IPO, we historically classified our convertible preferred stock warrant liabilities as Level 3. The convertible common stock warrant liabilities were valued using the Black-Scholes option-pricing model to determine the expected payout to calculate the fair value.

Revenue (Tables)

Revenue (Tables)	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Impact of Adopting ASC Topic 606	The impact from applying Topic 606 and Topic 340 as of and for the three and six months ended June 30, 2019 is as follows: Condensed Consolidated Statements of Operations Three Months Ended June 30, 2019 Six months ended June 30, 2019 As currently reported Impact of adopting new revenue standards As would have been reported under previous revenue standards As currently reported Impact of adopting new revenue standards As would have been reported under previous revenue standards (in thousands) Sales and marketing $ 16,906 $ (4 ) $ 16,902 $ 31,945 $ 67 $ 32,012 Total operating expenses 37,070 (4 ) 37,066 70,985 67 71,052 Loss from operations (11,681 ) 4 (11,677 ) (19,758 ) (67 ) (19,825 ) Loss before income taxes (15,505 ) 4 (15,501 ) (25,177 ) (67 ) (25,244 ) Net loss (15,587 ) 4 (15,583 ) (25,314 ) (67 ) (25,381 ) Comprehensive loss (15,594 ) 4 (15,590 ) (25,265 ) (67 ) (25,332 ) Net loss attributable to common stockholders $ (15,587 ) $ 4 $ (15,583 ) $ (25,314 ) $ (67 ) $ (25,381 ) Condensed Consolidated Balance Sheets As of June 30, 2019 As currently reported Impact of adopting new revenue standards As would have been reported under previous revenue standards (in thousands) Other assets $ 12,856 $ (5,794 ) $ 7,062 Total assets 356,376 (5,794 ) 350,582 Accumulated deficit (165,773 ) (5,794 ) (171,567 ) Total stockholders’ equity 267,322 (5,794 ) 261,528 Total liabilities and stockholders’ equity $ 356,376 $ (5,794 ) $ 350,582
Revenue by Geographic Area	The following table presents our net revenue by geographic region: Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 (in thousands) United States $ 32,521 $ 26,901 $ 65,943 $ 52,242 All other countries 13,652 7,547 25,786 14,704 Total revenue $ 46,173 $ 34,448 $ 91,729 $ 66,946
Revenue by Customer Type	The following table presents our net revenue for enterprise and non-enterprise customers: Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 (in thousands) Enterprise customers $ 39,421 $ 27,872 $ 78,465 $ 55,019 Non-enterprise customers 6,752 6,576 13,264 11,927 Total revenue $ 46,173 $ 34,448 $ 91,729 $ 66,946
Contract Assets and Liabilities	The following tables present our contract assets, contract liabilities and certain information related to these balances as of and for the three and six months ended June 30, 2019 : As of June 30, 2019 As of January 1, 2019 (in thousands) Contract liabilities (1) $ 653 $ 1,622 __________ (1) Balance as of January 1, 2019 represents contract liabilities as adjusted for Topic 606. Three months ended Six months ended (in thousands) Revenue recognized in the period from: Amounts included in contract liability at the beginning of the period $ 1,069 $ 2,006
Costs to Obtain Contracts	As of June 30, 2019 and January 1, 2019, our costs to obtain contracts were as follows: As of June 30, 2019 As of January 1, 2019 (in thousands) Deferred commissions (1) $ 6,514 $ 5,727 __________ (1) Balance as of January 1, 2019 represents deferred commissions as adjusted for Topic 606.

Investments and Fair Value Me_2

Investments and Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Schedule of Cash, Cash Equivalents, and Marketable Securities	Our total cash, cash equivalents and marketable securities consisted of the following: As of June 30, As of December 31, 2019 2018 (in thousands) Cash and cash equivalents: Cash $ 1,098 $ 32,546 Money market funds 212,365 2,419 U.S. Treasury securities — 1,998 Total cash and cash equivalents $ 213,463 $ 36,963 Marketable securities: Corporate notes and bonds $ 11,510 $ 12,852 Commercial paper 10,761 20,086 U.S. Treasury securities 2,994 5,932 Asset-backed securities 6,891 7,809 Total marketable securities $ 32,156 $ 46,679
Schedule of Available-For-Sale Investments	The following table summarizes adjusted cost, gross unrealized gains and losses, and fair value related to available-for-sale securities classified as marketable securities on the accompanying Condensed Consolidated Balance Sheets as of June 30, 2019 and December 31, 2018 : As of June 30, 2019 Amortized Gross Gross Fair (in thousands) Corporate notes and bonds $ 11,496 $ 14 $ — $ 11,510 Commercial paper 10,761 — — 10,761 U.S. Treasury securities 2,993 1 — 2,994 Asset-backed securities 6,888 3 — 6,891 Total available-for-sale investments $ 32,138 $ 18 $ — $ 32,156 As of December 31, 2018 Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Fair Value (in thousands) Corporate notes and bonds $ 12,867 $ — $ (15 ) $ 12,852 Commercial paper 20,086 — — 20,086 U.S. Treasury securities 5,933 — (1 ) 5,932 Asset-backed securities 7,817 — (8 ) 7,809 Total available-for-sale investments $ 46,703 $ — $ (24 ) $ 46,679
Financial Assets and Liabilities Measured and Recorded at Fair Value on a Recurring Basis	Financial assets and liabilities measured and recorded at fair value on a recurring basis consisted of the following types of instruments: As of June 30, 2019 Level 1 Level 2 Level 3 Total (in thousands) Cash equivalents: Money market funds $ 212,365 $ — $ — $ 212,365 Total cash equivalents 212,365 — — 212,365 Marketable securities: Corporate notes and bonds — 11,510 — 11,510 Commercial paper — 10,761 — 10,761 U.S. Treasury securities — 2,994 — 2,994 Asset-backed securities — 6,891 — 6,891 Total marketable securities — 32,156 — 32,156 Total financial assets $ 212,365 $ 32,156 $ — $ 244,521 As of December 31, 2018 Level 1 Level 2 Level 3 Total (in thousands) Cash equivalents: Money market funds $ 2,419 $ — $ — $ 2,419 U.S. Treasury securities — 1,998 — 1,998 Total cash equivalents 2,419 1,998 — 4,417 Marketable securities: Corporate notes and bonds — 12,852 — 12,852 Commercial paper — 20,086 — 20,086 U.S. Treasury securities — 5,932 — 5,932 Asset-backed securities — 7,809 — 7,809 Total marketable securities — 46,679 — 46,679 Total financial assets $ 2,419 $ 48,677 $ — $ 51,096 Convertible preferred stock warrant liabilities $ — $ — $ 3,261 $ 3,261 Total financial liabilities $ — $ — $ 3,261 $ 3,261
Summary of the Changes in the Fair Value of Level 3 Liabilities	The following table sets forth a summary of the changes in the fair value of our Level 3 financial liabilities: 2019 (in thousands) Fair value, December 31, 2018 $ 3,261 Change in fair value of Level 3 financial liabilities 2,404 Conversion of convertible preferred stock warrants into Class B common stock warrants (5,665 ) Fair value, June 30, 2019 $ —

Balance Sheet Information (Tabl

Balance Sheet Information (Tables)	6 Months Ended
	Jun. 30, 2019
Balance Sheet Related Disclosures [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consisted of the following: As of June 30, As of December 31, 2019 2018 (in thousands) Computer and networking equipment $ 83,236 $ 65,060 Leasehold improvements 3,268 3,259 Furniture and fixtures 559 539 Office equipment 535 513 Internal-use software 10,311 8,604 Property and equipment, gross 97,909 77,975 Accumulated depreciation and amortization (42,299 ) (35,621 ) Property and equipment, net $ 55,610 $ 42,354
Schedule of Accrued Liabilities	Accrued expenses consisted of the following: As of June 30, As of December 31, 2019 2018 (in thousands) Accrued computer and networking equipment $ 7,752 $ — Accrued compensation and related benefits 5,495 3,952 Sales and use tax payable 3,273 3,077 Accrued colocation and bandwidth costs 2,499 3,049 Other accrued liabilities 6,082 5,457 Total accrued expenses $ 25,101 $ 15,535

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in the Carrying Amount of Goodwill	The changes in the carrying amount of goodwill for the six months ended June 30, 2019 are as follows: Six months ended (in thousands) Balance as of December 31, 2018 $ 360 Foreign currency translation (1 ) Balance as of June 30, 2019 $ 359
Schedule of Intangible Assets	As of June 30, 2019 and December 31, 2018 , our intangible assets consisted of the following: As of June 30, 2019 As of December 31, 2018 Gross carrying value Accumulated amortization Net carrying value Gross carrying value Accumulated amortization Net carrying value (in thousands) Finite-lived intangible assets Internet protocol addresses $ 1,448 $ (289 ) $ 1,159 $ 852 $ (242 ) $ 610 Domain name 39 — 39 — — — Total finite-lived intangible assets $ 1,487 $ (289 ) $ 1,198 $ 852 $ (242 ) $ 610
Expected Amortization Expense of Intangible Assets	The annual expected amortization expense of intangible assets subject to amortization as of June 30, 2019 is as follows: As of June 30, 2019 (in thousands) Remainder of 2019 $ 75 2020 158 2021 158 2022 155 2023 145 Thereafter 507 Total $ 1,198

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Carrying Values of Debt Agreements	The following table reflects the carrying values of the debt agreements as of June 30, 2019 and December 31, 2018 : As of June 30, As of December 31, 2019 2018 (in thousands) Liability component: Principal amount—Second Amendment to Amended and Restated Loan and Security Agreement $ 44,167 $ 49,167 Less: unamortized debt issuance costs (68 ) (1,896 ) Less: current portion of long-term debt (30,000 ) (10,000 ) Long-term debt, less current portion—Second Amendment to Amended and Restated Loan and Security Agreement $ 14,099 $ 37,271 Principal amount—Capital Lease Agreement 6,601 3,538 Less: current portion of long-term debt (2,822 ) (1,370 ) Long-term debt, less current portion—Capital Lease Agreement $ 3,779 $ 2,168 Total long-term debt, less current portion $ 17,878 $ 39,439
Schedule of Contractual Future Repayments	Contractual future repayments for the above as of June 30, 2019 are as follows: Principal Interest Total (in thousands) Remainder of 2019 $ 26,393 $ 1,178 $ 27,571 2020 12,899 1,290 14,189 2021 11,404 404 11,808 2022 72 1 73 Total $ 50,768 $ 2,873 $ 53,641

Common Stock Warrant Liabilit_2

Common Stock Warrant Liabilities (Tables)	6 Months Ended
	Jun. 30, 2019
Warrants and Rights Note Disclosure [Abstract]
Convertible Common Stock Warrant Liabilities	The fair value of the warrants as of May 17, 2019 was estimated using the following assumptions: Series B Series C Series D Series F Total Fair value (in thousands) $ 1,818 $ 792 $ 668 $ 2,387 $ 5,665 Expected remaining term (in years) 4.46 5.47 7.21 9.62 Risk-free interest rate 2.17 % 2.20 % 2.27 % 2.37 % Expected volatility 39.0 % 39.3 % 40.2 % 42.4 % Dividend yield — — — — The fair value of the warrants as of December 31, 2018 was estimated using the following assumptions: Series B Series C Series D Series F Total Fair value (in thousands) $ 857 $ 407 $ 358 $ 1,639 $ 3,261 Expected remaining term (in years) 4.84 5.84 7.59 10.00 Risk-free interest rate 2.62 % 2.62 % 2.62 % 2.80 % Expected volatility 50.0 % 50.0 % 50.0 % 50.0 % Dividend yield — — — —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Purchase Commitments	The minimum future commitments related to cost of revenue related agreements as of June 30, 2019 were as follows. Cost of Revenue Commitments (in thousands) Remainder of 2019 $ 33,104 2020 17,591 2021 4,796 2022 968 Total $ 56,459

Convertible Preferred Stock (Ta

Convertible Preferred Stock (Tables)	6 Months Ended
	Jun. 30, 2019
Temporary Equity Disclosure [Abstract]
Schedule of Preferred Stock Outstanding	A summary of the Preferred Stock outstanding as of December 31, 2018 and other related information is as follows: As of December 31, 2018 Shares Authorized Shares Issued and Outstanding Net Carrying Amount Liquidation Preference (in thousands except share data) Series Seed Preferred Stock 8,049,365 8,049,364 $ 1,200 $ 1,200 Series A Preferred Stock 2,733,520 2,733,518 1,050 1,050 Series B Preferred Stock 11,058,835 10,945,209 11,260 11,260 Series C Preferred Stock 9,805,905 9,753,060 41,420 41,527 Series D Preferred Stock 11,675,463 11,627,903 74,912 75,000 Series E Preferred Stock 6,609,032 6,609,030 49,863 50,000 Series F Preferred Stock 4,216,523 3,912,129 39,879 40,000 Total 54,148,643 53,630,213 $ 219,584 $ 220,037

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Stockholders' Equity Note [Abstract]
Schedule of Stock Option Activity	The following table summarizes stock option activity during the six months ended June 30, 2019 : Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term Aggregate Intrinsic Value (in thousands) (in years) (in thousands) Outstanding at December 31, 2018 12,210 $ 2.96 7.80 $ 64,590 Granted 2,119 9.19 Exercised (1,418 ) 2.15 Cancelled/forfeited (568 ) 4.52 Outstanding at June 30, 2019 12,343 $ 4.04 7.72 $ 200,448 Vested and exercisable at June 30, 2019 7,305 $ 2.34 6.73 $ 131,052
Schedule of Unvested Exercised Options	The activity of non-vested shares as a result of early exercise of options granted to employees and non-employees, is as follows: Six months ended June 30, 2019 2018 (in thousands) Beginning balance 245 138 Early exercise of options 117 — Vested (81 ) (48 ) Repurchased — (11 ) Ending balance 281 79
Employee Stock Options, Valuation Assumptions		We estimated the fair value of stock option awards during the six months ended June 30, 2019 and 2018 on the date of the grant using the Black-Scholes option pricing model with the following weighted-average assumptions: Six months ended June 30, 2019 2018 Fair value of common stock $ 11.14 $ 4.05 Expected term (in years) 6.02 6.09 Risk-free interest rate 2.45 % 2.76 % Expected volatility 39.6 % 41.3 % Dividend yield — % — %
Employee Stock Purchase Plan, Valuation Assumptions	We estimated the fair value of shares granted under the ESPP on the first date of the offering period using the Black-Scholes option pricing model with the following assumptions: Six months ended June 30, 2019 2018 Fair value of common stock $ 6.92 N/A Expected term (in years) 0.50 N/A Risk-free interest rate 2.35 % N/A Expected volatility 36.4 % N/A Dividend yield — % N/A
Schedule of Stock-Based Compensation Expense	The following table summarizes the components of total stock-based compensation expense included in the accompanying Condensed Consolidated Statements of Operations and Comprehensive Loss: Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 (in thousands) Stock-based compensation expense by caption: Cost of revenue $ 293 $ 71 $ 437 $ 123 Research and development 714 324 1,146 600 Sales and marketing 596 226 965 451 General and administrative 640 369 1,162 664 Total $ 2,243 $ 990 $ 3,710 $ 1,838

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The shares issued in the IPO, the shares issued pursuant to the exercise by the underwriters of an option to purchase additional shares, and the shares of Class A and Class B common stock issued upon conversion of the outstanding shares of convertible preferred stock in the IPO are included in the table below weighted for the period outstanding: Three months ended June 30, 2019 2018 Class A Class B Class A (1) Class B (2) (in thousands, except per share amounts) Net loss $ (1,685 ) $ (13,902 ) N/A $ (5,836 ) Net loss attributable to common stockholders $ (1,685 ) $ (13,902 ) N/A $ (5,836 ) Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted 6,464 53,317 N/A 24,127 Net loss per share attributable to common stockholders, basic and diluted $ (0.26 ) $ (0.26 ) N/A $ (0.24 ) Six months ended June 30, 2019 2018 Class A Class B Class A (1) Class B (2) (in thousands, except per share amounts) Net loss $ (1,931 ) $ (23,383 ) N/A $ (15,142 ) Net loss attributable to common stockholders $ (1,931 ) $ (23,383 ) N/A $ (15,142 ) Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted 3,250 39,349 N/A 24,034 Net loss per share attributable to common stockholders, basic and diluted $ (0.59 ) $ (0.59 ) N/A $ (0.63 ) __________ (1) Class A common stock includes the issuance of 12.9 million shares of Class A common stock issued by us in connection with our IPO and shares issued upon the exercise of options subsequent to our IPO. (2) Class B common stock includes, for all periods presented, the conversion of all of our preferred stock into an aggregate of 53.6 million shares of our Class B common stock upon closing of the IPO.
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The potential shares of common stock that were excluded from the computation of diluted net loss per share attributable to common stockholders for the period presented because including them would have been antidilutive are as follows: Number of Shares As of June 30, 2019 2018 (in thousands) Convertible preferred stock — 53,550 Stock options 12,343 10,928 Early exercised stock options 281 79 Convertible common stock warrants 259 — Convertible preferred stock warrants — 214 Shares issuable pursuant to the ESPP 60 — Total 12,943 64,771

Information About Revenue and_2

Information About Revenue and Geographic Areas (Tables)	6 Months Ended
	Jun. 30, 2019
Segment Reporting [Abstract]
Schedule of Long-Lived Assets by Geographic Region	The following table presents long-lived assets by geographic region: As of June 30, As of December 31, 2019 2018 (in thousands) United States $ 36,723 $ 28,723 All other countries 18,887 13,631 Total long-lived assets $ 55,610 $ 42,354

Nature of Business (Details)

Nature of Business (Details) $ / shares in Units, $ in Thousands	May 21, 2019USD ($)$ / sharesshares	May 03, 2019	Jun. 30, 2019locationshares	Jun. 30, 2019USD ($)locationshares	Jun. 30, 2018USD ($)shares
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Points of presence | location			64	64
Common stock, stock split ratio		0.5
Class of Stock [Line Items]
Proceeds from initial public offering, net of underwriting fees | $				$ 192,510	$ 0
Common Class A
Class of Stock [Line Items]
Shares issued (in shares)					12,900,000
Common Class B
Class of Stock [Line Items]
Number of shares converted (in shares)					53,600,000
Convertible securities, conversion ratio			1	1
IPO | Common Class A
Class of Stock [Line Items]
Shares issued (in shares)	12,937,500
Common stock price per share (in dollars per share) | $ / shares	$ 16
Proceeds from initial public offering, net of underwriting fees | $	$ 192,500
Over-Allotment Option | Common Class A
Class of Stock [Line Items]
Shares issued (in shares)	1,687,500
Proceeds from initial public offering, net of underwriting fees | $				$ 25,100
Common Stock | Common Class A
Class of Stock [Line Items]
Shares issued (in shares)			12,937,500	12,937,500
Common Stock | Common Class B
Class of Stock [Line Items]
Number of shares converted (in shares)			53,630,213	53,630,213

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit	$ (165,773)		$ (146,186)
Impact of adopting new revenue standards | ASC Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit	$ (5,794)	$ 5,700

Revenue - Narrative (Details)

Revenue - Narrative (Details) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Remaining performance obligations	$ 65,500,000	$ 65,500,000
Accumulated deficit	$ (165,773,000)	$ (165,773,000)		$ (146,186,000)
Capitalized contract cost, amortization period	5 years	5 years
Enterprise customer threshold	$ 100,000	$ 100,000
Amortization of deferred sales commissions	600,000	1,100,000
ASC Topic 606 | Impact of adopting new revenue standards
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit	$ (5,794,000)	$ (5,794,000)	$ 5,700,000

Revenue - Adoption of ASC Topic

Revenue - Adoption of ASC Topic 606 (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Condensed Consolidated Statements of Operations
Sales and marketing	$ 16,906	$ 11,973	$ 31,945	$ 24,316
Total operating expenses	37,070	24,202	70,985	50,226
Loss from operations	(11,681)	(5,449)	(19,758)	(14,359)
Loss before income taxes	(15,505)	(5,801)	(25,177)	(15,049)
Net loss	(15,587)	(5,836)	(25,314)	(15,142)
Net loss attributable to common stockholders	(15,594)	(5,874)	(25,265)	(15,120)
Net loss attributable to common stockholders	(15,587)	(5,836)	(25,314)	(15,142)
Condensed Consolidated Balance Sheets
Other assets	12,856		12,856				$ 2,163
Assets	356,376		356,376				162,754
Accumulated deficit	(165,773)		(165,773)				(146,186)
Total stockholders’ equity (deficit)	267,322	$ (119,506)	267,322	$ (119,506)	$ (133,598)		(131,927)	$ (115,189)	$ (107,006)
Total liabilities and stockholders’ equity	356,376		356,376				$ 162,754
As would have been reported under previous revenue standards
Condensed Consolidated Statements of Operations
Sales and marketing	16,902		32,012
Total operating expenses	37,066		71,052
Loss from operations	(11,677)		(19,825)
Loss before income taxes	(15,501)		(25,244)
Net loss	(15,583)		(25,381)
Net loss attributable to common stockholders	(15,590)		(25,332)
Net loss attributable to common stockholders	(15,583)		(25,381)
Condensed Consolidated Balance Sheets
Other assets	7,062		7,062
Assets	350,582		350,582
Accumulated deficit	(171,567)		(171,567)
Total stockholders’ equity (deficit)	261,528		261,528
Total liabilities and stockholders’ equity	350,582		350,582
ASC Topic 606 | Impact of adopting new revenue standards
Condensed Consolidated Statements of Operations
Sales and marketing	(4)		67
Total operating expenses	(4)		67
Loss from operations	4		(67)
Loss before income taxes	4		(67)
Net loss	4		(67)
Net loss attributable to common stockholders	4		(67)
Net loss attributable to common stockholders	4		(67)
Condensed Consolidated Balance Sheets
Other assets	(5,794)		(5,794)
Assets	(5,794)		(5,794)
Accumulated deficit	(5,794)		(5,794)			$ 5,700
Total stockholders’ equity (deficit)	(5,794)		(5,794)
Total liabilities and stockholders’ equity	$ (5,794)		$ (5,794)

Revenue - Revenue by Geographic

Revenue - Revenue by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 46,173	$ 34,448	$ 91,729	$ 66,946
United States
Disaggregation of Revenue [Line Items]
Revenue	32,521	26,901	65,943	52,242
All other countries
Disaggregation of Revenue [Line Items]
Revenue	$ 13,652	$ 7,547	$ 25,786	$ 14,704

Revenue - Revenue by Customer T

Revenue - Revenue by Customer Type (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 46,173	$ 34,448	$ 91,729	$ 66,946
Enterprise customers
Disaggregation of Revenue [Line Items]
Revenue	39,421	27,872	78,465	55,019
Non-enterprise customers
Disaggregation of Revenue [Line Items]
Revenue	$ 6,752	$ 6,576	$ 13,264	$ 11,927

Revenue - Contract Assets and L

Revenue - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jan. 01, 2019
Revenue from Contract with Customer [Abstract]
Contract liabilities	$ 653	$ 653	$ 1,622
Revenue recognized in the period from:
Amounts included in contract liability at the beginning of the period	$ 1,069	$ 2,006

Revenue - Costs to Obtain Contr

Revenue - Costs to Obtain Contracts (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019
Revenue from Contract with Customer [Abstract]
Deferred sales commissions	$ 6,514	$ 5,727

Revenue - Remaining Performance

Revenue - Remaining Performance Obligation (Details) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-07-01	Jun. 30, 2019
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, timing of satisfaction	12 months
Remaining performance obligation, percentage	52.00%

Investments and Fair Value Me_3

Investments and Fair Value Measurements - Cash, Cash Equivalent and Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents	$ 213,463	$ 36,963	$ 61,433
Marketable securities	32,156	46,679
Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Marketable securities	11,510	12,852
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Marketable securities	10,761	20,086
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Marketable securities	2,994	5,932
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Marketable securities	6,891	7,809
Cash
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents	1,098	32,546
Money market funds
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents	212,365	2,419
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents	$ 0	$ 1,998

Investments and Fair Value Me_4

Investments and Fair Value Measurements - Available-For-Sale Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 32,138	$ 46,703
Gross Unrealized Gain	18	0
Gross Unrealized Loss	0	(24)
Fair Value	32,156	46,679
Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	11,496	12,867
Gross Unrealized Gain	14	0
Gross Unrealized Loss	0	(15)
Fair Value	11,510	12,852
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	10,761	20,086
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Fair Value	10,761	20,086
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,993	5,933
Gross Unrealized Gain	1	0
Gross Unrealized Loss	0	(1)
Fair Value	2,994	5,932
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	6,888	7,817
Gross Unrealized Gain	3	0
Gross Unrealized Loss	0	(8)
Fair Value	$ 6,891	$ 7,809

Investments and Fair Value Me_5

Investments and Fair Value Measurements - Narrative (Details) - security	Jun. 30, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Securities in a continuous loss position (in securities)	0	0

Investments and Fair Value Me_6

Investments and Fair Value Measurements - Assets and Liabilities at Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2019	May 17, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 212,365		$ 4,417
Marketable securities	32,156		46,679
Total financial assets	244,521		51,096
Convertible warrant liabilities	0	$ 5,665	3,261
Total financial liabilities			3,261
Corporate notes and bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	11,510		12,852
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	10,761		20,086
U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	2,994		5,932
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	6,891		7,809
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	212,365		2,419
U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents			1,998
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	212,365		2,419
Marketable securities	0		0
Total financial assets	212,365		2,419
Convertible warrant liabilities			0
Total financial liabilities			0
Level 1 | Corporate notes and bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0		0
Level 1 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0		0
Level 1 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0		0
Level 1 | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0		0
Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	212,365		2,419
Level 1 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents			0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0		1,998
Marketable securities	32,156		46,679
Total financial assets	32,156		48,677
Convertible warrant liabilities			0
Total financial liabilities			0
Level 2 | Corporate notes and bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	11,510		12,852
Level 2 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	10,761		20,086
Level 2 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	2,994		5,932
Level 2 | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	6,891		7,809
Level 2 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0		0
Level 2 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents			1,998
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0		0
Marketable securities	0		0
Total financial assets	0		0
Convertible warrant liabilities			3,261
Total financial liabilities			3,261
Level 3 | Corporate notes and bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0		0
Level 3 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0		0
Level 3 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0		0
Level 3 | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0		0
Level 3 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 0		0
Level 3 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents			$ 0

Investments and Fair Value Me_7

Investments and Fair Value Measurements - Level 3 Liabilities (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of level 3 investments, beginning balance	$ 0	$ 3,261
Change in fair value of Level 3 financial liabilities	2,404
Conversion of convertible preferred stock warrants into Class B common stock warrants	(5,665)
Fair value of level 3 investments, ending balance	$ 0

Balance Sheet Information - Pro

Balance Sheet Information - Property and equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 97,909	$ 77,975
Accumulated depreciation and amortization	(42,299)	(35,621)
Property and equipment, net	55,610	42,354
Computer and networking equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	83,236	65,060
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,268	3,259
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	559	539
Office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	535	513
Internal-use software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	10,311	8,604
Property and equipment, net	$ 6,000	$ 5,400

Balance Sheet Information - Nar

Balance Sheet Information - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 3,900	$ 3,300	$ 7,624	$ 6,295
Property and equipment, net	55,610		55,610		$ 42,354
Internal-use software
Property, Plant and Equipment [Line Items]
Depreciation and amortization	500	$ 400	1,000	$ 800
Property and equipment, net	$ 6,000		$ 6,000		$ 5,400

Balance Sheet Information - Acc

Balance Sheet Information - Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Accrued computer and networking equipment	$ 7,752	$ 0
Accrued compensation and related benefits	5,495	3,952
Sales and use tax payable	3,273	3,077
Accrued colocation and bandwidth costs	2,499	3,049
Other accrued liabilities	6,082	5,457
Total accrued expenses	$ 25,101	$ 15,535

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Goodwill (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 360
Foreign currency translation	(1)
Goodwill, ending balance	$ 359

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 26,300	$ 21,300	$ 47,600	$ 42,600
Internet protocol addresses
Finite-Lived Intangible Assets [Line Items]
Intangible assets purchased	600,000		600,000
Domain name
Finite-Lived Intangible Assets [Line Items]
Intangible assets purchased	$ 38,800		$ 38,800

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	$ 1,487	$ 852
Accumulated amortization	(289)	(242)
Total finite-lived intangible assets	1,198	610
Internet protocol addresses
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	1,448	852
Accumulated amortization	(289)	(242)
Total finite-lived intangible assets	1,159	610
Domain name
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	39	0
Accumulated amortization	0	0
Total finite-lived intangible assets	$ 39	$ 0

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets - Expected Amortization of Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Remainder of 2019	$ 75
2020	158
2021	158
2022	155
2023	145
Thereafter	507
Total finite-lived intangible assets	$ 1,198	$ 610

Debt - Loan and Security Agreem

Debt - Loan and Security Agreement (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Nov. 30, 2017	Aug. 31, 2016	Nov. 30, 2014	Sep. 30, 2013	Jul. 31, 2013
Debt Instrument [Line Items]
Amount of debt outstanding	$ 44,167,000		$ 44,167,000		$ 49,167,000
Interest expense	3,000,000	$ 400,000	4,200,000	$ 700,000
Loan and Security Agreement
Debt Instrument [Line Items]
Debt facility, maximum borrowing amount						$ 30,000,000	$ 17,500,000	$ 15,000,000	$ 5,000,000	$ 2,500,000
Amount of debt outstanding	$ 24,200,000		$ 24,200,000		$ 29,200,000
Line of Credit | Loan and Security Agreement | Prime Rate
Debt Instrument [Line Items]
Basis spread on variable rate			1.75%

Debt - Mezzanine Loan and Secur

Debt - Mezzanine Loan and Security Agreement (Details) - USD ($)	Jun. 30, 2019	Aug. 31, 2016
Mezzanine Loan and Security Agreement
Debt Instrument [Line Items]
Debt facility, maximum borrowing amount		$ 12,500,000
Line-of-credit facility, minimum advance amount		$ 2,500,000
Line of Credit | Mezzanine Loan and Security Agreement
Debt Instrument [Line Items]
Interest rate, stated percentage	11.75%
Line of Credit | Senior Loan Agreement
Debt Instrument [Line Items]
Maximum increase in interest rate in case of default	5.00%
Covenant, minimum adjusted quick ratio	1.15
Covenant, minimum monthly revenue as a percentage of budget	0.80
Covenant, minimum unrestricted cash balance	$ 10,000,000

Debt - Capital Lease Agreement

Debt - Capital Lease Agreement (Details) - USD ($)	Feb. 01, 2019	Mar. 31, 2019	Jun. 30, 2019	Feb. 28, 2019	Dec. 31, 2018	Mar. 31, 2018	Jun. 30, 2017
Debt Instrument [Line Items]
Capital lease obligations			$ 6,601,000		$ 3,538,000
Capital Lease Obligations
Debt Instrument [Line Items]
Debt Instrument, Term	3 years	3 years	4 years
Capital Lease Obligations | Network equipment
Debt Instrument [Line Items]
Interest rate, stated percentage		5.38%				5.38%	5.24%
Capital lease, face amount		$ 1,300,000		$ 2,900,000		$ 500,000	$ 5,000,000

Debt - Credit Facility (Details

Debt - Credit Facility (Details)	6 Months Ended
	Jun. 30, 2019USD ($)	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
Amount of debt outstanding	$ 44,167,000	$ 49,167,000
Second Lien Credit Facility
Debt Instrument [Line Items]
Debt facility, maximum borrowing amount		30,000,000
Amount of debt outstanding	$ 20,000,000	$ 20,000,000
Line of Credit | Second Lien Credit Facility
Debt Instrument [Line Items]
Covenant, minimum monthly revenue as a percentage of budget	0.75
Line of Credit | Second Lien Credit Facility | Prime Rate
Debt Instrument [Line Items]
Basis spread on variable rate	4.25%

Debt - Carrying Values of Debt

Debt - Carrying Values of Debt Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
Principal amount—Second Amendment to Amended and Restated Loan and Security Agreement	$ 44,167	$ 49,167
Less: unamortized debt issuance costs	(68)	(1,896)
Less: current portion of long-term debt	30,000	10,000
Long-term debt, less current portion—Second Amendment to Amended and Restated Loan and Security Agreement	14,099	37,271
Principal amount—Capital Lease Agreement	6,601	3,538
Less: current portion of long-term debt	(2,822)	(1,370)
Long-term debt, less current portion—Capital Lease Agreement	3,779	2,168
Total long-term debt, less current portion	$ 17,878	$ 39,439

Debt - Maturities Schedule (Det

Debt - Maturities Schedule (Details) $ in Thousands	Jun. 30, 2019USD ($)
Principal
Principal - Remainder of 2019	$ 26,393
Principal - 2020	12,899
Principal - 2021	11,404
Principal - 2022	72
Principal - Total	50,768
Interest
Interest - Remainder of 2019	1,178
Interest - 2020	1,290
Interest - 2021	404
Interest - 2022	1
Interest - Total	2,873
Total
Total - Remainder of 2019	27,571
Total - 2020	14,189
Total - 2021	11,808
Total - 2022	73
Total	$ 53,641

Common Stock Warrant Liabilit_3

Common Stock Warrant Liabilities (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019USD ($)shares	Jun. 30, 2019USD ($)shares	May 17, 2019USD ($)	Dec. 31, 2018USD ($)
Class of Warrant or Right [Line Items]
Convertible warrant liabilities	$ 0	$ 0	$ 5,665	$ 3,261
Common Stock Warrants, Series B
Class of Warrant or Right [Line Items]
Convertible warrant liabilities			1,818	857
Common Stock Warrants, Series C
Class of Warrant or Right [Line Items]
Convertible warrant liabilities			792	407
Common Stock Warrants, Series D
Class of Warrant or Right [Line Items]
Convertible warrant liabilities			668	358
Common Stock Warrants, Series F
Class of Warrant or Right [Line Items]
Convertible warrant liabilities			$ 2,387	$ 1,639
Expected remaining term (in years) | Common Stock Warrants, Series B
Class of Warrant or Right [Line Items]
Expected remaining term			4 years 5 months 15 days	4 years 10 months 2 days
Expected remaining term (in years) | Common Stock Warrants, Series C
Class of Warrant or Right [Line Items]
Expected remaining term			5 years 5 months 19 days	5 years 10 months 2 days
Expected remaining term (in years) | Common Stock Warrants, Series D
Class of Warrant or Right [Line Items]
Expected remaining term			7 years 2 months 15 days	7 years 7 months 2 days
Expected remaining term (in years) | Common Stock Warrants, Series F
Class of Warrant or Right [Line Items]
Expected remaining term			9 years 7 months 13 days	10 years
Risk-free interest rate | Common Stock Warrants, Series B
Class of Warrant or Right [Line Items]
Measurement input			0.0217	0.0262
Risk-free interest rate | Common Stock Warrants, Series C
Class of Warrant or Right [Line Items]
Measurement input			0.0220	0.0262
Risk-free interest rate | Common Stock Warrants, Series D
Class of Warrant or Right [Line Items]
Measurement input			0.0227	0.0262
Risk-free interest rate | Common Stock Warrants, Series F
Class of Warrant or Right [Line Items]
Measurement input			0.0237	0.0280
Expected volatility | Common Stock Warrants, Series B
Class of Warrant or Right [Line Items]
Measurement input			0.390	0.500
Expected volatility | Common Stock Warrants, Series C
Class of Warrant or Right [Line Items]
Measurement input			0.393	0.500
Expected volatility | Common Stock Warrants, Series D
Class of Warrant or Right [Line Items]
Measurement input			0.402	0.500
Expected volatility | Common Stock Warrants, Series F
Class of Warrant or Right [Line Items]
Measurement input			0.424	0.500
Dividend yield | Common Stock Warrants, Series B
Class of Warrant or Right [Line Items]
Measurement input			0	0
Dividend yield | Common Stock Warrants, Series C
Class of Warrant or Right [Line Items]
Measurement input			0	0
Dividend yield | Common Stock Warrants, Series D
Class of Warrant or Right [Line Items]
Measurement input			0	0
Dividend yield | Common Stock Warrants, Series F
Class of Warrant or Right [Line Items]
Measurement input			0	0
Common Stock | Common Class B
Class of Warrant or Right [Line Items]
Exercise of common stock warrants (in shares) | shares	172,380	172,380

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Rent expense	$ 1.8	$ 1.7	$ 3.5	$ 3.5
Sublease income	$ 0.3	$ 0.2	$ 0.6	$ 0.5

Commitments and Contingencies_2

Commitments and Contingencies - Purchase Commitments (Details) $ in Thousands	Jun. 30, 2019USD ($)
Commitments and Contingencies Disclosure [Abstract]
Remainder of 2019	$ 33,104
2020	17,591
2021	4,796
2022	968
Total	$ 56,459

Convertible Preferred Stock (De

Convertible Preferred Stock (Details) $ / shares in Units, $ in Thousands	Jun. 30, 2019USD ($)shares	Dec. 31, 2018USD ($)series_of_stock$ / sharesshares
Temporary Equity [Line Items]
Number of Preferred Stock series | series_of_stock		7
Preferred Series par value (in dollars per share) | $ / shares		$ 0.00002
Shares authorized (in shares)		54,148,643
Shares issued (in shares)		53,630,213
Shares outstanding (in shares)	0	53,630,213
Net Carrying Amount | $	$ 0	$ 219,584
Liquidation Preference | $		$ 220,037
Series Seed Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares)		8,049,365
Shares issued (in shares)		8,049,364
Shares outstanding (in shares)		8,049,364
Net Carrying Amount | $		$ 1,200
Liquidation Preference | $		$ 1,200
Series A Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares)		2,733,520
Shares issued (in shares)		2,733,518
Shares outstanding (in shares)		2,733,518
Net Carrying Amount | $		$ 1,050
Liquidation Preference | $		$ 1,050
Series B Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares)		11,058,835
Shares issued (in shares)		10,945,209
Shares outstanding (in shares)		10,945,209
Net Carrying Amount | $		$ 11,260
Liquidation Preference | $		$ 11,260
Series C Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares)		9,805,905
Shares issued (in shares)		9,753,060
Shares outstanding (in shares)		9,753,060
Net Carrying Amount | $		$ 41,420
Liquidation Preference | $		$ 41,527
Series D Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares)		11,675,463
Shares issued (in shares)		11,627,903
Shares outstanding (in shares)		11,627,903
Net Carrying Amount | $		$ 74,912
Liquidation Preference | $		$ 75,000
Series E Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares)		6,609,032
Shares issued (in shares)		6,609,030
Shares outstanding (in shares)		6,609,030
Net Carrying Amount | $		$ 49,863
Liquidation Preference | $		$ 50,000
Series F Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares)		4,216,523
Shares issued (in shares)		3,912,129
Shares outstanding (in shares)		3,912,129
Net Carrying Amount | $		$ 39,879
Liquidation Preference | $		$ 40,000

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock and Preferred Stock (Details)	Jun. 30, 2019shares	May 31, 2019vote$ / sharesshares	Dec. 31, 2018shares
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)		10,000,000
Preferred stock, par value (in dollars per share) | $ / shares		$ 0.00002
Common Class A
Class of Stock [Line Items]
Common stock, shares authorized (in shares)		1,000,000,000
Common stock, par value (in dollars per share) | $ / shares		$ 0.00002
Common stock, voting rights (votes per share) | vote		1
Common stock, shares issued (in shares)	12,995,158
Common stock, shares outstanding (in shares)	12,995,158
Common Class B
Class of Stock [Line Items]
Common stock, shares authorized (in shares)		94,129,050
Common stock, par value (in dollars per share) | $ / shares		$ 0.00002
Common stock, voting rights (votes per share) | vote		10
Common stock, shares issued (in shares)	80,433,917		25,026,001
Common stock, shares outstanding (in shares)	80,433,917		25,026,001

Stockholders' Equity - Equity I

Stockholders' Equity - Equity Incentive Plans (Details) - USD ($)	1 Months Ended	6 Months Ended
	May 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Shares issuable pursuant to the ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares reserved for future issuance (in shares)		2,500,000
Maximum deduction of eligible compensation	15.00%
Maximum purchase value during offering period, per employee	$ 25,000
Stock plan offering period		6 months
Purchase price of common stock, percentage of fair value		85.00%
2011 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares reserved for future issuance (in shares)		23,578,923	21,689,410
Common stock, shares available for future issuance		0	609,804
2011 Equity Incentive Plan | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period		10 years
Award vesting period		4 years
Award vesting percentage per year		25.00%
2019 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares reserved for future issuance (in shares)		14,400,000
2019 Equity Incentive Plan | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period	10 years
Award vesting period	4 years
Award vesting percentage per year	25.00%

Stockholders' Equity - Stock Op

Stockholders' Equity - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Jun. 30, 2019	Dec. 31, 2018
Stock Option Activity
Options outstanding, beginning balance (in shares)	12,210
Granted (in shares)	2,119
Exercised (in shares)	(1,418)
Cancelled/forfeited (in shares)	(568)
Options outstanding, ending balance (in shares)	12,343		12,210
Options vested and exercisable (in shares)				7,305
Stock Options Weighted Average Exercise Price
Options outstanding, weighted average exercise price, beginning of period (in dollars per share)	$ 4.04		$ 2.96	$ 4.04	$ 2.96
Granted, weighted average exercise price (in dollars per share)	9.19
Exercised, weighted average exercise price (in dollars per share)	2.15
Cancelled/forfeited, weighted average exercise price (in dollars per share)	4.52
Options outstanding, weighted average exercise price, end of period (in dollars per share)	$ 4.04		$ 2.96
Vested and exercisable, weighted-average exercise price (in dollars per share)				$ 2.34
Stock Option Activity, Additional Disclosures
Weighted-average remaining contractual period	7 years 8 months 19 days		7 years 9 months 18 days
Aggregate intrinsic value				$ 200,448	$ 64,590
Vested and exercisable, weighted average contractual term	6 years 8 months 23 days
Vested and exercisable, aggregate intrinsic value				$ 131,052
Pre-tax intrinsic value	$ 10,900	$ 1,100
Vesting of early exercised stock options	$ 2,800	$ 1,700
Weighted-average grant date fair value (in dollars per share)	$ 5.36	$ 1.95

Stockholders' Equity - Early Ex

Stockholders' Equity - Early Exercise of Stock Options (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance (in shares)	244,658	138,000
Early exercise of options (in shares)	117,000	0
Vested (in shares)	(81,000)	(48,000)
Repurchased (in shares)	0	(11,000)
Ending balance (in shares)	280,942	79,000
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Other long-term liabilities	$ 1.2		$ 1

Stockholders' Equity - Employee

Stockholders' Equity - Employee Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 2,243	$ 990	$ 3,710	$ 1,838
Unrecognized stock-based compensation cost	$ 19,600		$ 19,600
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of common stock (in shares)	$ 11.14	$ 4.05	$ 11.14	$ 4.05
Expected term (in years)			6 years 7 days	6 years 1 month 2 days
Risk-free interest rate			2.45%	2.76%
Expected volatility			39.60%	41.30%
Dividend yield			0.00%	0.00%
Stock-based compensation expense	$ 1,900	$ 1,000	$ 3,300	$ 1,800
Weighted-average period of recognition			3 years 1 month 6 days

Stockholders' Equity - Employ_2

Stockholders' Equity - Employee Stock Purchase Plan (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 2,243,000	$ 990,000	$ 3,710,000	$ 1,838,000
Shares issuable pursuant to the ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum employee contribution as a percentage of salary			15.00%
Fair value of common stock (in shares)	$ 6.92		$ 6.92
Expected term (in years)	15 days
Risk-free interest rate	2.35%
Expected volatility	36.40%
Dividend yield	0.00%
Contributions withheld for taxes			$ 800,000	0
Stock-based compensation expense			$ 400,000	$ 0
Stock issued under ESPP	0		0

Stockholders' Equity - Stock-ba

Stockholders' Equity - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 2,243	$ 990	$ 3,710	$ 1,838
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	293	71	437	123
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	714	324	1,146	600
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	596	226	965	451
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 640	$ 369	$ 1,162	$ 664

Net Loss Per Share Attributab_3

Net Loss Per Share Attributable to Common Stockholders - Computation of EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Class of Stock [Line Items]
Net loss	$ (15,587)	$ (5,836)	$ (25,314)	$ (15,142)
Net loss attributable to common stockholders	$ (15,587)	$ (5,836)	$ (25,314)	$ (15,142)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	59,781	24,127	42,599	24,034
Net loss per share attributable to common shareholders, basic and diluted (USD per share)	$ (0.26)	$ (0.24)	$ (0.59)	$ (0.63)
Common Class A
Class of Stock [Line Items]
Net loss	$ (1,685)		$ (1,931)
Net loss attributable to common stockholders	$ (1,685)		$ (1,931)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	6,464		3,250
Net loss per share attributable to common shareholders, basic and diluted (USD per share)	$ (0.26)		$ (0.59)
Shares issued (in shares)				12,900
Common Class B
Class of Stock [Line Items]
Net loss	$ (13,902)	$ (5,836)	$ (23,383)	$ (15,142)
Net loss attributable to common stockholders	$ (13,902)	$ (5,836)	$ (23,383)	$ (15,142)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	53,317	24,127	39,349	24,034
Net loss per share attributable to common shareholders, basic and diluted (USD per share)	$ (0.26)	$ (0.24)	$ (0.59)	$ (0.63)
Conversion of convertible preferred stock to Class B common stock (in shares)				53,600

Net Loss Per Share Attributab_4

Net Loss Per Share Attributable to Common Stockholders - Antidilutive Securities (Details) - shares shares in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	12,943	64,771
Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	0	53,550
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	12,343	10,928
Early exercised stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	281	79
Warrant
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	259	214
Shares issuable pursuant to the ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	60	0

Income Taxes (Details)

Income Taxes (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Income taxes	$ 82,000	$ 35,000	$ 137,000	$ 93,000

Information About Revenue and_3

Information About Revenue and Geographic Areas (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)segment	Dec. 31, 2018USD ($)
Segment Reporting [Abstract]
Number of reportable segments | segment	1
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 55,610	$ 42,354
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	36,723	28,723
All other countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 18,887	$ 13,631

Related Party Transactions (Det

Related Party Transactions (Details) - Related Party Promissory Note - Stockholder - USD ($)	1 Months Ended
	Jul. 31, 2016	Jun. 30, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Related party note receivable	$ 100,000
Number of shares converted (in shares)	53,125
Interest rate of promissory note	1.77%
Promissory note, amount outstanding		$ 0	$ 75,000

Subsequent Events (Details)

Subsequent Events (Details) - USD ($)	Jul. 08, 2019	Jun. 30, 2019	Dec. 31, 2018
Subsequent Event [Line Items]
Amount of debt outstanding		$ 44,167,000	$ 49,167,000
Second Lien Credit Facility
Subsequent Event [Line Items]
Debt facility, maximum borrowing amount			30,000,000
Amount of debt outstanding		$ 20,000,000	$ 20,000,000
Line of Credit | Second Lien Credit Facility | Subsequent Event
Subsequent Event [Line Items]
Payoff of line-of-credit	$ 20,000,000

Uncategorized Items - fsly-10qx

Label	Element	Value
Restricted Cash and Cash Equivalents	us-gaap_RestrictedCashAndCashEquivalents	$ 87,000
Restricted Cash and Cash Equivalents	us-gaap_RestrictedCashAndCashEquivalents	$ 0