Pure Storage (PSTG) 10-K 26 Mar 18 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Jan. 31, 2018	Mar. 20, 2018	Jul. 31, 2017
Document And Entity Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Jan. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Trading Symbol	PSTG
Entity Registrant Name	Pure Storage, Inc.
Entity Central Index Key	1,474,432
Current Fiscal Year End Date	--01-31
Entity Filer Category	Large Accelerated Filer
Entity Well-Known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 1.6
Class A common stock
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding (in shares)		162,727,090
Class B common stock
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding (in shares)		66,511,236

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jan. 31, 2018	Jan. 31, 2017
Current assets:
Cash and cash equivalents	$ 244,057	$ 183,675
Marketable securities	353,289	362,986
Accounts receivable, net of allowance of $2,000 and $1,062 as of January 31, 2017 and 2018	243,001	168,978
Inventory	34,497	23,498
Deferred commissions, current	22,437	15,787
Prepaid expenses and other current assets	47,552	25,157
Total current assets	944,833	780,081
Property and equipment, net	89,142	81,695
Intangible assets, net	5,057	6,560
Deferred income taxes, non-current	1,060	844
Other assets, non-current	39,315	30,565
Total assets	1,079,407	899,745
Current liabilities:
Accounts payable	84,420	52,719
Accrued compensation and benefits	59,898	39,252
Accrued expenses and other liabilities	26,829	21,697
Deferred revenue, current	209,377	158,095
Liability related to early exercised stock options	320	1,362
Total current liabilities	380,844	273,125
Deferred revenue, non-current	196,632	145,031
Other liabilities, non-current	4,025	3,159
Total liabilities	581,501	421,315
Commitments and contingencies (Note 5)
Stockholders’ equity:
Preferred stock, par value of $0.0001 per share— 20,000 shares authorized as of January 31, 2017 and 2018; no shares issued and outstanding as of January 31, 2017 and 2018	0	0
Class A and Class B common stock, par value of $0.0001 per share— 2,250,000 (Class A 2,000,000, Class B 250,000) shares authorized as of January 31, 2017 and 2018; 204,364 (Class A 87,027, Class B 117,337) and 220,979 (Class A 129,502, Class B 91,477) shares issued and outstanding as of January 31, 2017 and 2018	22	20
Additional paid-in capital	1,479,883	1,281,452
Accumulated other comprehensive loss	(1,917)	(562)
Accumulated deficit	(980,082)	(802,480)
Total stockholders’ equity	497,906	478,430
Total liabilities and stockholders’ equity	$ 1,079,407	$ 899,745

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jan. 31, 2018	Jan. 31, 2017
Accounts receivable, allowance	$ 1,062	$ 2,000
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	20,000,000	20,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, shares authorized (in shares)	2,250,000,000	2,250,000,000
Common stock, shares issued (in shares)	220,979,000	204,364,000
Common stock, shares outstanding (in shares)	220,979,000	204,364,000
Class A common stock
Common stock, par value per share (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	2,000,000,000	2,000,000,000
Common stock, shares issued (in shares)	129,502,242	87,027,000
Common stock, shares outstanding (in shares)	129,502,000	87,027,000
Class B common stock
Common stock, par value per share (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	250,000,000	250,000,000
Common stock, shares issued (in shares)	91,476,735	117,337,000
Common stock, shares outstanding (in shares)	91,477,000	117,337,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Revenue:
Product	$ 813,985	$ 590,001	$ 375,733
Support	209,034	137,976	64,600
Total revenue	1,023,019	727,977	440,333
Cost of revenue:
Product	275,242	194,150	132,870
Support	78,539	58,129	35,023
Total cost of revenue	353,781	252,279	167,893
Gross profit	669,238	475,698	272,440
Operating expenses:
Research and development	279,196	245,817	166,645
Sales and marketing	480,030	360,035	240,574
General and administrative	95,170	84,652	75,402
Legal settlement	0	30,000	0
Total operating expenses	854,396	720,504	482,621
Loss from operations	(185,158)	(244,806)	(210,181)
Other income (expense), net	11,445	1,627	(2,002)
Loss before provision for income taxes	(173,713)	(243,179)	(212,183)
Provision for income taxes	3,889	1,887	1,569
Net loss	$ (177,602)	$ (245,066)	$ (213,752)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.84)	$ (1.26)	$ (2.59)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	211,609	194,714	82,460

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (177,602)	$ (245,066)	$ (213,752)
Other comprehensive loss:
Change in unrealized net loss on available-for-sale securities	(1,355)	(562)	0
Comprehensive loss	$ (178,957)	$ (245,628)	$ (213,752)

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders’ Equity (Deficit) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (in shares) at Jan. 31, 2015	122,281
Beginning balance at Jan. 31, 2015	$ 543,940
Increase (Decrease) in Temporary Equity [Roll Forward]
Conversion of convertible preferred stock to common stock upon initial public offering (in shares)	(122,281)
Conversion of convertible preferred stock to common stock upon initial public offering	$ (543,940)
Ending balance (in shares) at Jan. 31, 2016	0
Ending balance at Jan. 31, 2016	$ 0
Beginning balance (in shares) at Jan. 31, 2015		36,465
Beginning balance at Jan. 31, 2015	(299,830)	$ 4	$ 41,749	$ 0	$ (341,583)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of convertible preferred stock to common stock upon initial public offering (in shares)		122,281
Conversion of convertible preferred stock to common stock upon initial public offering	543,940	$ 12	543,928
Issuance of common stock upon initial public offering, net of offering costs of $4,539 (in shares)		28,750
Issuance of common stock upon initial public offering, net of offering costs of $4,539	455,138	$ 3	455,135
Issuance of common stock to Pure Good Foundation (in shares)		700
Issuance of common stock to Pure Good Foundation	11,900		11,900
Issuance of common stock upon exercise of stock options, net of repurchases (in shares)		2,313
Issuance of common stock upon exercise of stock options, net of repurchases	6,008	$ 0	6,008
Stock-based compensation expense	58,225		58,225
Vesting of early exercised stock options	1,725		1,725
Net loss	(213,752)				(213,752)
Ending balance (in shares) at Jan. 31, 2016		190,509
Ending balance at Jan. 31, 2016	$ 563,354	$ 19	1,118,670	0	(555,335)
Ending balance (in shares) at Jan. 31, 2017	0
Ending balance at Jan. 31, 2017	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment from adoption of ASU 2016-09 | Accounting Standards Update 2016-09	0		2,079		(2,079)
Issuance of common stock upon exercise of stock options, net of repurchases (in shares)		10,180
Issuance of common stock upon exercise of stock options, net of repurchases	15,031	$ 1	15,030
Stock-based compensation expense	116,668		116,668
Vesting of early exercised stock options	3,399		3,399
Vesting of restricted stock units (in shares)		1,238
Vesting of restricted stock units	0	$ 0	0
Common stock issued under employee stock purchase plan (in shares)		2,437
Common stock issued under employee stock purchase plan	25,606		25,606
Other comprehensive income (loss)	(562)			(562)
Net loss	(245,066)				(245,066)
Ending balance (in shares) at Jan. 31, 2017		204,364
Ending balance at Jan. 31, 2017	$ 478,430	$ 20	1,281,452	(562)	(802,480)
Ending balance (in shares) at Jan. 31, 2018	0
Ending balance at Jan. 31, 2018	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options, net of repurchases (in shares)		8,814
Issuance of common stock upon exercise of stock options, net of repurchases	24,581	$ 1	24,580
Stock-based compensation expense	150,673		150,673
Vesting of early exercised stock options	1,042		1,042
Vesting of restricted stock units (in shares)		5,278
Vesting of restricted stock units	0	$ 1	(1)
Common stock issued under employee stock purchase plan (in shares)		2,523
Common stock issued under employee stock purchase plan	22,137		22,137
Other comprehensive income (loss)	(1,355)			(1,355)
Net loss	(177,602)				(177,602)
Ending balance (in shares) at Jan. 31, 2018		220,979
Ending balance at Jan. 31, 2018	$ 497,906	$ 22	$ 1,479,883	$ (1,917)	$ (980,082)

Consolidated Statements of Con7

Consolidated Statements of Convertible Preferred Stock and Stockholders’ Equity (Deficit) (Parenthetical) $ in Thousands	12 Months Ended
	Jan. 31, 2017USD ($)
Common Stock
Offering costs	$ 4,539

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (177,602)	$ (245,066)	$ (213,752)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	61,744	50,203	32,254
Stock-based compensation expense	150,673	116,668	58,225
Contribution of common stock to the Pure Good Foundation	0	0	11,900
Other	2,054	1,584	(1,093)
Changes in operating assets and liabilities:
Accounts receivable, net	(74,505)	(44,049)	(67,292)
Inventory	(12,595)	(3,776)	1,481
Deferred commissions	(11,997)	(740)	(13,021)
Prepaid expenses and other assets	(23,799)	(6,133)	(8,704)
Accounts payable	29,278	10,644	24,901
Accrued compensation and other liabilities	26,622	19,381	24,710
Deferred revenue	102,883	86,922	142,535
Net cash provided by (used in) operating activities	72,756	(14,362)	(7,856)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of property and equipment	(65,060)	(76,773)	(39,355)
Purchase of intangible assets	0	(1,000)	0
Purchases of marketable securities	(202,656)	(526,717)	0
Sales of marketable securities	66,489	114,354	0
Maturities of marketable securities	144,068	48,513	0
Net increase in restricted cash	(2,029)	(5,600)	(2,485)
Net cash used in investing activities	(59,188)	(447,223)	(41,840)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from initial public offering, net of issuance costs	0	0	459,425
Net proceeds from exercise of stock options	24,677	14,912	6,008
Proceeds from issuance of common stock under employee stock purchase plan	22,137	25,606	0
Payments of deferred offering costs	0	0	(3,702)
Net cash provided by financing activities	46,814	40,518	461,731
Net increase (decrease) in cash and cash equivalents	60,382	(421,067)	412,035
Cash and cash equivalents, beginning of period	183,675	604,742	192,707
Cash and cash equivalents, end of period	244,057	183,675	604,742
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Cash paid for income taxes	3,090	2,866	1,118
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION
Conversion of convertible preferred stock to common stock upon initial public offering	0	0	543,940
Property and equipment purchased but not yet paid	9,940	7,414	6,212
Vesting of early exercised stock options	1,042	3,399	1,725
Unpaid deferred offering costs	$ 0	$ 0	$ 546

Business Overview

Business Overview	12 Months Ended
	Jan. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business Overview	Business Overview Organization and Description of Business Pure Storage, Inc. (the Company, we, us, or other similar pronouns) was originally incorporated in the state of Delaware in October 2009 under the name OS76, Inc. In January 2010, we changed our name to Pure Storage, Inc. We are building a data platform that transforms business through a dramatic increase in performance and reduction in complexity and costs. We are headquartered in Mountain View, California and have wholly owned subsidiaries throughout the world. Initial Public Offering In October 2015, we completed our initial public offering (IPO) of Class A common stock, in which we sold 28,750,000 shares. The shares were sold at an IPO price of $17.00 per share for net proceeds of $459.4 million , after deducting underwriting discounts and commissions of $29.3 million but before deducting offering costs of $4.5 million . Upon the closing of our IPO, all outstanding shares of our convertible preferred stock automatically converted into 122,280,679 shares of Class B common stock. Following the IPO, we have two classes of authorized common stock – Class A common stock and Class B common stock.

Basis of Presentation and Summa

Basis of Presentation and Summary of Significant Accounting Policies	12 Months Ended
	Jan. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	Basis of Presentation and Summary of Significant Accounting Policies Principles of Consolidation The consolidated financial statements include the accounts of the company and our wholly owned subsidiaries and have been prepared in conformity with accounting principles generally accepted in the United States (U.S. GAAP). All intercompany balances and transactions have been eliminated in consolidation. Foreign Currency The functional currency of our foreign subsidiaries is the U.S. dollar. Transactions denominated in currencies other than the functional currency are remeasured to the functional currency at the average exchange rate in effect during the period. At the end of each reporting period, monetary assets and liabilities are remeasured using exchange rates in effect at the balance sheet date. Non-monetary assets and liabilities are remeasured at historical exchange rates. Foreign currency transaction gains and losses are recorded in other income (expense), net in the consolidated statements of operations. For the years ended January 31, 2016 , 2017 and 2018 , we recorded net foreign currency transaction losses of $2.3 million, $2.6 million, and a net foreign currency transaction gain of $6.0 million, respectively. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported and disclosed in the financial statements and accompanying notes. Actual results could differ from these estimates. Such estimates include, but are not limited to, the determination of best estimate of selling price included in multiple-deliverable revenue arrangements, sales commissions, useful lives of intangible assets and property and equipment, fair values of stock-based awards, provision for income taxes, including related reserves, and contingent liabilities, among others. Management bases its estimates on historical experience and on various other assumptions which management believes to be reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities. Concentration Risk Financial instruments that are exposed to concentration of credit risk consist primarily of cash and cash equivalents and accounts receivable. As of January 31, 2017 and 2018 , substantially all of our cash and cash equivalents have been invested with three financial institutions and such deposits exceed federally insured limits. Management believes that the financial institutions that hold our investments are financially sound and, accordingly, are subject to minimal credit risk. We define a customer as an end user that purchases our products and services from one of our channel partners or from us directly. Our revenue and accounts receivable are derived substantially from the United States across a multitude of industries. We perform ongoing evaluations to determine customer credit. As of January 31, 2017 , we had one channel partner that represented 10% or more of total accounts receivable on that date. As of January 31, 2018 , no channel partner represented 10% or more of total accounts receivable on that date. No single channel partner represented 10% or more of revenue for the years ended January 31, 2016 and 2018. One channel partner represented 11% of revenue for the year ended January 31, 2017. No end customer represented 10% or more of revenue for the years ended January 31, 2016 , 2017 and 2018 . We rely on a limited number of suppliers for our contract manufacturing and certain raw material components. In instances where suppliers fail to perform their obligations, we may be unable to find alternative suppliers or satisfactorily deliver our products to our customers on time. Cash and Cash Equivalents Cash and cash equivalents consist of cash in banks and highly liquid investments, primarily money market accounts, purchased with an original maturity of three months or less. Marketable Securities We classify our marketable securities as available-for-sale at the time of purchase and reevaluate such classification at each balance sheet date. We may sell these securities at any time for use in current operations even if they have not yet reached maturity. As a result, we classify our securities, including those with maturities beyond twelve months, as current assets in the consolidated balance sheets. We carry these securities at fair value and record unrealized gains and losses in other comprehensive income (loss), which is reflected as a component of stockholders' equity. We evaluate our securities to assess whether those with unrealized loss positions are other than temporarily impaired. We consider impairments to be other than temporary if they are related to deterioration in credit risk or if it is likely we will sell the securities before the recovery of their cost basis. Realized gains and losses from the sale of marketable securities and declines in value deemed to be other than temporary are determined based on the specific identification method. Realized gains and losses are reported in other income (expense), net in the consolidated statements of operations. Fair Value of Financial Instruments The carrying value of our financial instruments, including cash equivalents, accounts receivable, accounts payable and accrued liabilities, approximates fair value. Accounts Receivable and Allowance Accounts receivable are recorded at the invoiced amount, and stated at realizable value, net of an allowance for doubtful accounts. Credit is extended to customers based on an evaluation of their financial condition and other factors. We generally do not require collateral or other security to support accounts receivable. We perform ongoing credit evaluations of our customers and maintain an allowance for doubtful accounts. We assess the collectability of the accounts by taking into consideration the aging of our trade receivables, historical experience, and management judgment. We write off trade receivables against the allowance when management determines a balance is uncollectible and no longer actively pursues collection of the receivable. The following table presents the changes in the allowance for doubtful accounts: Year Ended January 31, 2016 2017 2018 (in thousands) Allowance for doubtful accounts, beginning balance $ 210 $ 944 $ 2,000 Provision, net 918 1,394 482 Writeoffs (184 ) (338 ) (1,420 ) Allowance for doubtful accounts, ending balance $ 944 $ 2,000 $ 1,062 Restricted Cash Restricted cash is comprised of cash collateral for letters of credit related to our leases and for a vendor credit card program. As of January 31, 2017 and 2018 , we had restricted cash of $12.7 million and $14.8 million , which was included in other assets, non-current in the consolidated balance sheets. Inventory Inventory consists of finished goods and component parts, which are purchased from contract manufacturers. Product demonstration units, which we regularly sell, are the primary component of our inventories. Inventories are stated at the lower of cost or net realizable value. Cost is determined using the specific identification method for finished goods and weighted-average method for component parts. We account for excess and obsolete inventory by reducing the carrying value to the estimated net realizable value of the inventory based upon management’s assumptions about future demand and market conditions. In addition, we record a liability for firm, non-cancelable and unconditional purchase commitments with contract manufacturers and suppliers for quantities in excess of future demand forecasts consistent with excess and obsolete inventory valuations. As of January 31, 2018 , we did not record any liability related to the above. Inventory write-offs were insignificant for the years ended January 31, 2016 , 2017 and 2018 . Property and Equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization is computed using the straight-line method over the estimated useful lives of the respective assets (test equipment— 2 years , computer equipment and software— 2 to 3 years , furniture and fixtures— 7 years ). Leasehold improvements are amortized over the shorter of their estimated useful lives or the remaining lease term . Depreciation commences once the asset is placed in service. Intangible Assets Intangible assets are stated at cost, net of accumulated amortization. We amortize our intangible assets on a straight-line basis over an estimated useful life of five to seven years. During the year ended January 31, 2017, we acquired certain technology patents for $1.0 million , which are amortized on a straight-line basis over an estimated useful life of five years. Impairment of Long-Lived Assets We review our long-lived assets, including property and equipment, and finite-lived intangible assets for impairment whenever events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. We measure the recoverability of these assets by comparing the carrying amounts to the future undiscounted cash flows the assets are expected to generate. If the total of the future undiscounted cash flows is less than the carrying amount of an asset, we record an impairment charge for the amount by which the carrying amount of the asset exceeds its fair market value. There have been no impairment charges recorded in any of the periods presented in the consolidated financial statements. Deferred Commissions Deferred commissions consist of direct and incremental costs paid to our sales force related to customer contracts. The deferred commission amounts are recoverable through the revenue streams that will be recognized under the related customer contracts. Direct sales commissions are deferred when earned and amortized over the same period that revenue is recognized from the related customer contract. Amortization of deferred commissions is included in sales and marketing expense in the consolidated statements of operations. As of January 31, 2017 and 2018 , we recorded deferred commissions, current, of $15.8 million and $22.4 million , and deferred commissions, non-current, of $14.9 million and $20.3 million , within other assets, non-current in the consolidated balance sheets. During the years ended January 31, 2016 , 2017 and 2018 , we recognized sales commission expenses of $47.2 million , $84.8 million , and $119.8 million , respectively. Revenue Recognition We derive revenue from two sources: (1) product revenue which includes hardware and embedded software and (2) support revenue which includes customer support, hardware maintenance and software upgrades on a when-and-if-available basis. We recognize revenue when: • Persuasive evidence of an arrangement exists —We rely upon sales agreements and/or purchase orders to determine the existence of an arrangement. • Delivery has occurred —We typically recognize product revenue upon shipment, as title and risk of loss are transferred to our channel partners at that time. Products are typically shipped directly by us to customers, and our channel partners do not stock our inventory. • The fee is fixed or determinable —We assess whether the fee is fixed or determinable based on the payment terms associated with the transaction. • Collection is reasonably assured —We assess collectability based on credit analysis and payment history. Our product revenue is derived from the sale of hardware and operating system software that is integrated into the hardware and therefore deemed essential to its functionality. The hardware and the operating system software essential to the functionality of the hardware are considered non-software deliverables and, therefore, are not subject to industry-specific software revenue recognition guidance. Support revenue is derived from the sale of maintenance and support agreements. Maintenance and support agreements include the right to receive unspecified software upgrades and enhancements on a when-and-if-available basis, bug fixes, parts replacement services related to the hardware, as well as access to our cloud-based management and support platform. Revenue related to maintenance and support agreements are recognized ratably over the contractual term, which generally range from one to five years. Costs related to maintenance and support agreements are expensed as incurred. In addition, our Evergreen Storage program provides our customers who continually maintain active maintenance and support for three years with an included controller refresh with each additional three year maintenance and support renewal. In accordance with multiple-element arrangement accounting guidance, the controller refresh represents an additional deliverable that is a separate unit of accounting and the allocated revenue is recognized in the period in which these controllers are shipped. Most of our arrangements, other than stand-alone renewals of maintenance and support agreements, are multiple-element arrangements with a combination of product and support related deliverables (as defined above). Under multiple-element arrangements, we allocate consideration at the inception of an arrangement to all deliverables based on the relative selling price method in accordance with the hierarchy provided by the multiple-element arrangement accounting guidance, which includes (i) vendor-specific objective evidence (VSOE), of selling price, if available; (ii) third-party evidence (TPE), of selling price, if VSOE is not available; and (iii) best estimate of selling price (BESP), if neither VSOE nor TPE is available. We allocate consideration to support related deliverables based on VSOE and to all other deliverables based on BESP as TPE typically cannot be obtained. • VSOE —We determine VSOE based on our historical pricing and discounting practices for the specific products and services when sold separately. In determining VSOE, we require that a substantial majority of the stand-alone selling prices fall within a reasonably narrow pricing range. • TPE —When VSOE cannot be established for deliverables in multiple-element arrangements, we apply judgment with respect to whether we can establish a selling price based on TPE. TPE is determined based on competitor prices for interchangeable products or services when sold separately to similarly situated customers. However, because our products contain a significant element of proprietary technology and our solutions offer substantially different features and functionality, the comparable pricing of products with similar functionality typically cannot be obtained. • BESP —When neither VSOE nor TPE can be established, we utilize BESP to allocate consideration to deliverables in a multiple-element arrangement. Our process to determine BESP for products and support is based on qualitative and quantitative considerations of multiple factors, which primarily include historical sales, margin objectives and discount behavior. Additional considerations are given to other factors such as customer demographics, costs to manufacture products or provide support, pricing practices and market conditions. Deferred Revenue Deferred revenue primarily consists of amounts that have been invoiced but that have not yet been recognized as revenue and primarily consists of support. The current portion of deferred revenue represents the amounts that are expected to be recognized as revenue within one year of the consolidated balance sheet date. Warranty Costs We generally provide a three -year warranty on hardware and a 90 -day warranty on our software embedded in the hardware. Our hardware warranty provides for parts replacement for defective components and our software warranty provides for bug fixes. Our maintenance and support agreement provides for the same parts replacement that customers are entitled to under our warranty program, except that replacement parts are delivered according to targeted response times to minimize disruption to our customers’ critical business applications. Substantially all customers purchase maintenance and support agreements. Therefore, given that substantially all our products sales are sold together with maintenance and support agreements, we generally do not have exposure related to warranty costs and no warranty reserve has been recorded. Research and Development Research and development costs are expensed as incurred. Research and development costs consist primarily of personnel costs including stock-based compensation expense, expensed prototype, to the extent there is no alternative use for that equipment, consulting services, depreciation of equipment used in research and development and allocated overhead costs. Software Development Costs We expense software development costs before technological feasibility is reached. We have determined that technological feasibility is reached shortly before the release of our products and as a result, the development costs incurred after the establishment of technological feasibility and before the release of those products have not been significant and accordingly, all software development costs have been expensed as incurred. Software development costs also include costs incurred related to our hosted applications used to deliver our support services. Capitalization begins when the preliminary project stage is complete, management with the relevant authority authorizes and commits to the funding of the software project, and it is probable the project will be completed and the software will be used to perform the intended function. Total costs related to our hosted applications incurred to date have been insignificant and as a result no software development costs were capitalized during the years ended January 31, 2016 , 2017 and 2018 . Advertising Expenses Advertising costs are expensed as incurred. Advertising expenses were $6.2 million , $10.7 million and $10.3 million for the years ended January 31, 2016 , 2017 and 2018 , respectively. Stock-Based Compensation Stock-based compensation includes expenses related to restricted stock units (RSUs), stock options and purchase rights issued to employees under our ESPP. We determine the fair value of our stock options under our equity plans and purchase rights issued to employees under our ESPP on the date of grant utilizing the Black-Scholes option pricing model, which is impacted by the fair value of our common stock, as well as changes in assumptions regarding a number of subjective variables. These variables include the expected common stock price volatility over the term of the awards, the expected term of the awards, risk-free interest rates and expected dividend yield. RSUs are measured at the fair market value of the underlying stock at the grant date. We recognize stock-based compensation expense for stock-based awards on a straight-line basis over the period during which an employee is required to provide services in exchange for the award (generally the vesting period of the award). Subsequent to the adoption of Accounting Standards Update (ASU) No. 2016-09 (ASU 2016-09) on February 1, 2016, we account for forfeitures as they occur. For stock-based awards granted to employees with a performance condition, we recognize stock-based compensation expense for these awards under the accelerated attribution method over the requisite service period when management determines it is probable that the performance condition will be satisfied. Income Taxes We account for income taxes using the asset and liability method. Deferred income taxes are recognized by applying enacted statutory tax rates applicable to future years to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. The measurement of deferred tax assets is reduced, if necessary, by a valuation allowance to amounts that are more likely than not to be realized. We recognize tax benefits from uncertain tax positions only if we believe that it is more likely than not that the tax position will be sustained on examination by the taxing authorities based on the technical merits of the position. The tax benefits recognized in the financial statements from such positions are then measured based on the largest benefit that has a greater than 50% likelihood of being realized upon settlement. Recent Accounting Pronouncements In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (ASU 2014-09 or ASC 606), requiring an entity to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those goods or services. ASC 606 will supersede nearly all existing revenue recognition guidance under U.S. GAAP when it becomes effective. The standard permits two methods of adoptions: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of applying the standard recognized at the date of application (cumulative catch-up transition method). We have adopted the standard using the full retrospective method beginning February 1, 2018, for the year ending January 31, 2019, and our historical financial information for the years ended January 31, 2017 and 2018 will be restated to conform to the new standard. The impact on our consolidated financial statements upon the adoption of the standard is primarily as follows: • An increase in total revenue of $11.2 million and $1.8 million for the years ended January 31, 2017 and 2018 (an increase in product revenue of $24.5 million and $20.5 million for the years ended January 31, 2017 and 2018 and a decrease in support revenue of $13.3 million and $18.7 million for the years ended January 31, 2017 and 2018), and a decrease in deferred revenue of $30.1 million and $31.9 million as of January 31, 2017 and 2018, due to the removal of limitation on contingent revenue; • A decrease in commission expense of $12.3 million and $16.0 million for the years ended January 31, 2017 and 2018, and an increase in deferred commissions of $28.2 million and $44.2 million as of January 31, 2017 and 2018, due to a change in amortization period from contract term (typically ranging from one to five years) to an expected useful life of six years; • A decrease in loss from operations of $23.5 million and $17.8 million for the years ended January 31, 2017 and 2018, due to the changes above. In addition, the adoption of the standard does not have a significant impact to the provision for income taxes on our consolidated statements of operations, nor does it impact net cash provided by or used in operating, investing, or financing activities on our consolidated statements of cash flows. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (ASU 2016-02). ASU 2016-02 requires lessees to recognize all leases with terms in excess of one year on their balance sheet as a right-of-use asset and a lease liability at the commencement date. The new standard also simplifies the accounting for sale and leaseback transactions. The amendments in this update will be effective for us beginning on February 1, 2019 and must be adopted using a modified retrospective method for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. Early adoption is permitted. We are currently evaluating adoption methods and the impact of this standard on our consolidated financial statements. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13). ASU 2016-13 amends guidance on reporting credit losses for assets held at amortized cost basis and available-for-sale debt securities to require that credit losses on available-for-sale debt securities be presented as an allowance rather than as a write-down. The measurement of credit losses for newly recognized financial assets and subsequent changes in the allowance for credit losses are recorded in the statements of operations. The amendments in this update will be effective for us beginning on February 1, 2020 with early adoption permitted on or after February 1, 2019. We are currently evaluating the impact of this standard on our consolidated financial statements. In August 2016, the FASB issued ASU No. 2016-15 (Topic 230) Statement of Cash Flow: Classification of Certain Cash Receipts and Cash Payments, which clarifies how companies present and classify certain cash receipts and cash payments in the statement of cash flows. This standard is effective for us beginning on February 1, 2018 and will be applied on a retrospective basis. We do not expect the adoption of this standard will have a significant impact on our consolidated financial statements. In October 2016, the FASB issued ASU No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory (ASU 2016-16), which requires the recognition of the income tax consequences of an intra-entity transfer of an asset, other than inventory, when the transfer occurs. ASU 2016-16 will be effective for us beginning on February 1, 2018 and will be applied on a modified retrospective basis. Early adoption is permitted. We do not expect the adoption of this standard will have a material impact our consolidated financial statements. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (ASU 2016-18), which requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. ASU 2016-18 will be effective for us beginning on February 1, 2018 and will be applied on a retrospective basis. We do not expect the adoption of this standard will have a significant impact on our cash flow activity presented on our consolidated statements of cash flows. In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718)-Scope of Modification Accounting, to clarify when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new standard, modification is required only if the fair value, the vesting conditions, or the classification of an award as equity or liability changes as a result of the change in terms or conditions. This standard will be effective for us beginning February 1, 2018 and will be applied on a prospective basis. We do not expect the adoption of this standard will have a significant impact on our consolidated financial statements. In February 2018, the FASB issued ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220) - Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. This standard allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act and requires certain disclosures about stranded tax effects. This standard will be effective for us beginning February 1, 2019 and should be applied either in the period of adoption or retrospectively. Early adoption is permitted. We are currently evaluating the impact of this standard on our consolidated financial statements. In March 2018, the FASB issued ASU No. 2018-05, Income Taxes (Topic 740) - Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118 ("ASU 2018-05"). This standard amends Accounting Standards Codification 740, Income Taxes (ASC 740) to provide guidance on accounting for the tax effects of the Tax Cuts and Jobs Act (the Tax Act) pursuant to Staff Accounting Bulletin No. 18, which allows companies to complete the accounting under ASC 740 within a one-year measurement period from the Tax Act enactment date. This standard is effective upon issuance. We are currently evaluating the impact of this standard on our consolidated financial statements. Reclassifications Certain amounts in prior periods have been reclassified to conform with current period presentation.

Financial Instruments

Financial Instruments	12 Months Ended
	Jan. 31, 2018
Fair Value Disclosures [Abstract]
Financial Instruments	Financial Instruments Fair Value Measurements We measure our cash equivalents, marketable securities and restricted cash at fair value on a recurring basis. We define fair value as the exchange price that would be received from sale of an asset or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. We measure our financial assets and liabilities at fair value at each reporting period using a fair value hierarchy which requires us to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. A financial instrument’s classification within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement. Three levels of inputs may be used to measure fair value: • Level I —Observable inputs are unadjusted quoted prices in active markets for identical assets or liabilities; • Level II —Observable inputs are quoted prices for similar assets and liabilities in active markets or inputs other than quoted prices that are observable for the assets or liabilities, either directly or indirectly through market corroboration, for substantially the full term of the financial instruments; and • Level III —Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. These inputs are based on our own assumptions used to measure assets and liabilities at fair value and require significant management judgment or estimation. We classify our cash equivalents, marketable securities and restricted cash within Level 1 or Level 2 because they are valued using either quoted market prices or inputs other than quoted prices which are directly or indirectly observable in the market, including readily-available pricing sources for the identical underlying security which may not be actively traded. Our fixed income available-for-sale securities consist of high quality, investment grade securities from diverse issuers. The valuation techniques used to measure the fair value of our marketable securities were derived from non-binding market consensus prices that are corroborated by observable market data and quoted market prices for similar instruments. Cash Equivalents, Marketable Securities and Restricted Cash The following tables summarize our cash equivalents, marketable securities and restricted cash by significant investment categories as of January 31, 2017 and 2018 (in thousands): January 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Cash Equivalents Marketable Securities Restricted Cash Level 1 Money market accounts $ — $ — $ — $ 12,734 $ — $ — $ 12,734 Level 2 U.S. government treasury notes 148,298 22 (289 ) 148,031 13,226 134,805 — U.S. government agencies 40,398 2 (159 ) 40,241 — 40,241 — Corporate debt securities 185,701 242 (379 ) 185,564 — 185,564 — Foreign government bonds 2,377 2 (3 ) 2,376 — 2,376 — Total $ 376,774 $ 268 $ (830 ) $ 388,946 $ 13,226 $ 362,986 $ 12,734 January 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Cash Equivalents Marketable Securities Restricted Cash Level 1 Money market accounts $ — $ — $ — $ 32,057 $ 17,294 $ — $ 14,763 Level 2 U.S. government treasury notes 131,643 — (651 ) 130,992 10,172 120,820 — U.S. government agencies 47,229 — (333 ) 46,896 — 46,896 — Corporate debt securities 186,506 116 (1,049 ) 185,573 — 185,573 — Total $ 365,378 $ 116 $ (2,033 ) $ 395,518 $ 27,466 $ 353,289 $ 14,763 The amortized cost and estimated fair value of our marketable securities are shown below by contractual maturity (in thousands): January 31, 2018 Amortized Cost Fair Value Due within one year $ 173,537 $ 173,278 Due in one to five years 181,669 180,011 Total $ 355,206 $ 353,289 Based on our evaluation of available evidence, we concluded that the gross unrealized losses on our marketable securities as of January 31, 2018 were temporary in nature. The following table presents gross unrealized losses and fair values for those investments that were in a continuous unrealized loss position as of January 31, 2018 , aggregated by investment category (in thousands): Less than 12 months Greater than 12 months Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss U.S. government treasury notes $ 68,212 $ (219 ) $ 52,607 $ (432 ) $ 120,819 $ (651 ) U.S. government agencies 23,004 (156 ) 23,892 (177 ) 46,896 (333 ) Corporate debt securities 117,165 (732 ) 33,132 (317 ) 150,297 (1,049 ) Total $ 208,381 $ (1,107 ) $ 109,631 $ (926 ) $ 318,012 $ (2,033 ) Gross realized gains and losses on sale of marketable securities were immaterial for the years ended January 31, 2017 and 2018 .

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Jan. 31, 2018
Balance Sheet Components Disclosure [Abstract]
Balance Sheet Components	Balance Sheet Components Inventory Inventory consists of the following (in thousands): January 31, 2017 2018 Raw materials $ 3,003 $ 1,181 Finished goods 20,495 33,316 Inventory $ 23,498 $ 34,497 Property and Equipment, Net Property and equipment, net consists of the following (in thousands): January 31, 2017 2018 Test equipment $ 105,955 $ 142,311 Computer equipment and software 54,521 72,329 Furniture and fixtures 4,494 5,363 Leasehold improvements 10,332 15,032 Total property and equipment 175,302 235,035 Less: accumulated depreciation and amortization (93,607 ) (145,893 ) Property and equipment, net $ 81,695 $ 89,142 Depreciation and amortization expense related to property and equipment was $31.0 million , $48.8 million and $60.2 million for the years ended January 31, 2016 , 2017 and 2018 , respectively. Intangible Assets, Net Intangible assets, net consist of the following (in thousands): January 31, 2017 2018 Technology patents $ 10,125 $ 10,125 Accumulated amortization (3,565 ) (5,068 ) Intangible assets, net $ 6,560 $ 5,057 Intangible assets amortization expense was $1.3 million , $1.4 million and $1.5 million for the years ended January 31, 2016 , 2017 and 2018 , respectively. The weighted-average remaining useful life of the technology patents is 3.4 years. Due to the defensive nature of these patents, the amortization is included in general and administrative expenses in the consolidated statements of operations. As of January 31, 2018 , expected future amortization expense for intangible assets is as follows (in thousands): Year Ending January 31, Estimated Future 2019 $ 1,504 2020 1,504 2021 1,504 2022 545 Total $ 5,057 Accrued Expenses and Other Liabilities Accrued expenses and other liabilities consist of the following (in thousands): January 31, 2017 2018 Taxes payable $ 1,675 $ 4,052 Accrued marketing 6,718 5,928 Accrued travel and entertainment expenses 2,235 4,386 Other accrued liabilities 11,069 12,463 Total accrued expenses and other liabilities $ 21,697 $ 26,829

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Jan. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Operating Leases We lease our office facilities under operating lease agreements expiring through April 2026. Certain of these lease agreements have escalating rent payments. We recognize rent expense under such agreements on a straight-line basis over the lease term, and the difference between the rent paid and the straight-line rent is recorded in accrued expenses and other liabilities and other long-term liabilities in the accompanying consolidated balance sheets. In August 2017, we entered into a seven -year operating lease for approximately 45,831 square feet of office space in Mountain View, California with a total rent obligation and management fees of $32.2 million . In March 2018, we amended our Mountain View, California lease signed in August 2017 to add a ten -year lease for additional 31,571 square feet of office space for a total rent obligation and management fees of approximately $34.8 million , which are excluded from the table below. In connection with this lease amendment, we issued a letter of credit of $1.5 million . As of January 31, 2018 , the aggregate future minimum payments under non-cancelable operating leases consist of the following (in thousands): Year Ending January 31, Operating Leases 2019 $ 19,321 2020 18,627 2021 20,083 2022 17,250 2023 13,991 Thereafter 23,727 Total $ 112,999 Rent expense recognized under our operating leases were $11.0 million , $16.6 million and $19.4 million for the years ended January 31, 2016 , 2017 and 2018 , respectively. Purchase Obligations As of January 31, 2017 and 2018 , we had $4.1 million and $26.8 million of non-cancelable contractual purchase obligations related to certain software service and other contracts. Letters of Credit In connection with the lease executed in August 2017, we issued a letter of credit of $2.6 million . As of January 31, 2017 and 2018 , we had letters of credit in the aggregate amount of $7.7 million and $9.6 million , in connection with our facility leases. The letters of credit are collateralized by restricted cash and mature at various dates through August 2026 . Legal Matters On October 18, 2016, we entered into an agreement with Dell Inc. (Dell), as successor-in-interest to EMC to settle all litigation between EMC and us. The terms of the settlement include a payment to Dell, the dismissal of all litigation between the parties, mutual releases, and a license to the disputed patent. Accordingly, we paid Dell a one-time settlement amount of $30.0 million , and all litigation between EMC and us was dismissed prior to October 31, 2016. We evaluated the settlement as a multiple-element arrangement, which requires us to allocate the one-time payment to the identifiable elements based on their relative fair values. Based on our estimates of fair value, we determined that the sole benefit of the settlement is to avoid further litigation costs with no value attributable to future use or benefit. Accordingly, we recorded the $30.0 million as a legal settlement charge in general and administrative expenses during the three months ended October 31, 2016. From time to time, we have become involved in claims and other legal matters arising in the normal course of business. We investigate these claims as they arise. Although claims are inherently unpredictable, we currently are not aware of any matters that may have a material adverse effect on our business, financial position, results of operations or cash flows. Accordingly, we have not recorded any material loss contingency on our consolidated balance sheet as of January 31, 2018 . Indemnification Our arrangements generally include certain provisions for indemnifying customers against liabilities if our products or services infringe a third party’s intellectual property rights. Other guarantees or indemnification arrangements include guarantees of product and service performance and standby letters of credit for lease facilities. It is not possible to determine the maximum potential amount under these indemnification obligations due to the limited history of prior indemnification claims and the unique facts and circumstances involved in each particular agreement. To date, we have not incurred any material costs as a result of such obligations and have not accrued any liabilities related to such obligations in the consolidated financial statements. In addition, we indemnify our officers, directors and certain key employees while they are serving in good faith in their respective capacities. To date, there have been no claims under any indemnification provisions.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Jan. 31, 2018
Equity [Abstract]
Stockholders’ Equity	Stockholders’ Equity Preferred Stock Upon the closing of our IPO in October 2015, we filed an Amended and Restated Certificate of Incorporation, which authorized 20,000,000 shares of undesignated preferred stock, the rights, preferences and privileges of which may be designated from time to time by our board of directors. As of January 31, 2018 , there were no shares of preferred stock issued or outstanding. Class A and Class B Common Stock We have two classes of authorized common stock, Class A common stock and Class B common stock. As of January 31, 2018 , we had 2,000,000,000 shares of Class A common stock authorized with a par value of $0.0001 per share and 250,000,000 shares of Class B common stock authorized with a par value of $0.0001 per share. As of January 31, 2018 , 129,502,242 shares of Class A common stock were issued and outstanding and 91,476,735 shares of Class B common stock were issued and outstanding. The rights of the holders of Class A and Class B common stock are identical, except with respect to voting. Each share of Class A common stock is entitled to one vote per share. Each share of Class B common stock is entitled to 10 votes per share. Shares of Class B common stock may be converted to Class A common stock at any time at the option of the stockholder. Shares of Class B common stock automatically convert to Class A common stock upon the following: (i) sale or transfer of such share of Class B common stock; (ii) the death of the Class B common stockholder (or nine months after the date of death if the stockholder is one of our founders); and (iii) on the final conversion date, defined as the earlier of (a) the first trading day on or after the date on which the outstanding shares of Class B common stock represent less than 10% of the then outstanding Class A and Class B common stock; (b) the ten th anniversary of the IPO; or (c) the date specified by vote of the holders of a majority of the outstanding shares of Class B common stock, voting as a single class. Class A and Class B common stock are referred to as common stock throughout the notes to the consolidated financial statements, unless otherwise noted. In August 2015, we established the Pure Good Foundation as a non-profit organization, and in September 2015 we issued 700,000 shares of our Class B common stock to this foundation. As a result, we incurred a one-time general and administrative expense of $11.9 million during the year ended January 31, 2016, the amount of which was equal to the fair value of the shares of Class B common stock issued. Common Stock Reserved for Issuance As of January 31, 2018 , we had reserved shares of common stock for future issuance as follows: January 31, 2018 Shares underlying outstanding stock options 46,359,949 Shares underlying outstanding restricted stock units 17,682,646 Shares reserved for future equity awards 19,684,916 Shares reserved for future employee stock purchase plan awards 2,489,767 Total 86,217,278

Equity Incentive Plans

Equity Incentive Plans	12 Months Ended
	Jan. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity Incentive Plans	Equity Incentive Plans Equity Incentive Plans We maintain two equity incentive plans: the 2009 Equity Incentive Plan (our 2009 Plan) and the 2015 Equity Incentive Plan (our 2015 Plan). In August 2015, our board of directors adopted, and in September 2015 our stockholders approved, the 2015 Plan, which became effective in connection with our IPO in October 2015 and serves as the successor to our 2009 Plan. Our 2015 Plan provides for the issuance of incentive stock options to our employees and non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance stock awards, performance cash awards, and other forms of stock awards to our employees, directors and consultants. No new awards are issued under our 2009 Plan after the effective date of our 2015 Plan. Outstanding awards granted under our 2009 Plan will remain subject to the terms of our 2009 Plan and applicable award agreements, until such outstanding awards that are stock options are exercised, terminated or expired by their terms. We have initially reserved 27,000,000 shares of our Class A common stock for issuance under our 2015 Plan. The number of shares reserved for issuance under our 2015 Plan increases automatically on the first day of February of each of 2016 through 2025, in an amount equal to 5% of the total number of shares of our capital stock outstanding as of the immediately preceding January 31. The exercise price of stock options will generally not be less than 100% of the fair market value of our common stock on the date of grant, as determined by our board of directors. Our equity awards generally vest over a two to four year period and expire no later than ten years from the date of grant. 2015 Employee Stock Purchase Plan In August 2015, our board of directors adopted and our stockholders approved, the 2015 Employee Stock Purchase Plan (2015 ESPP), which became effective in connection with our IPO. A total of 3,500,000 shares of Class A common stock was initially reserved for issuance under the 2015 ESPP. The number of shares reserved for issuance under our 2015 ESPP increases automatically on the first day of February of each of 2016 through 2025, in an amount equal to the lesser of (i) 1% of the total number of shares of our capital stock outstanding as of the immediately preceding January 31, and (ii) 3,500,000 shares of Class A common stock. The 2015 ESPP allows eligible employees to purchase shares of our Class A common stock at a discount through payroll deductions of up to 30% of their eligible compensation, subject to a cap of 3,000 shares on any purchase date or $25,000 in any calendar year (as determined under applicable tax rules). Except for the initial offering period, the 2015 ESPP provides for 24 month offering periods beginning March 16th and September 16th of each year, and each offering period will consist of four six -month purchase periods, subject to a reset provision. If the closing stock price on the offering date of a new offering falls below the closing stock price on the offering date of an ongoing offering, the ongoing offering would terminate immediately following the purchase of ESPP shares on the purchase date immediately preceding the new offering and participants in the terminated ongoing offering would automatically be enrolled in the new offering (ESPP reset). On each purchase date, eligible employees will purchase our Class A common stock at a price per share equal to 85% of the lesser of the fair market value of our Class A common stock (1) on the first trading day of the applicable offering period or (2) the purchase date. Since inception, we had two ESPP resets. The first ESPP reset occurred when our closing stock price on March 16, 2016 was below the closing stock price on October 7, 2015, which triggered a new 24 -month offering period through March 15, 2018, resulting in a modification charge of approximately $10.6 million to be recognized over the new offering period. The second ESPP reset occurred when our closing stock price on March 16, 2017 was below the closing stock prices on March 16, 2016 and September 16, 2016, which triggered a new 24 -month offering period through March 15, 2019, resulting in another modification charge of approximately $9.0 million . This amount along with the remaining unamortized expense from the first reset, is being recognized over the new offering period ending March 15, 2019. During the years ended January 31, 2016, 2017 and 2018, we recognized $4.4 million , $18.3 million and $18.3 million , respectively, of stock-based compensation expense related to our 2015 ESPP. As of January 31, 2018 , there was $26.4 million of unrecognized stock-based compensation expense related to our 2015 ESPP which is expected to be recognized over a weighted-average period of approximately 1.1 years. Early Exercise of Stock Options Certain employees and directors have exercised options granted under the 2009 Plan prior to vesting. The unvested shares are subject to a repurchase right held by us at the original purchase price. The proceeds initially are recorded as liability related to early exercised stock options and reclassified to additional paid-in capital as the repurchase right lapses. No unvested stock options were exercised during the years ended January 31, 2016, 2017 and 2018. In the year ended January 31, 2016, we repurchased 15,000 shares of unvested common stock related to early exercised stock options at the original purchase price due to the termination of an employee. No shares were repurchased during the years ended January 31, 2017 and 2018. As of January 31, 2017 and 2018, 494,117 and 85,262 shares held by employees and directors were subject to repurchase at an aggregate price of $1.4 million and $0.3 million . Stock Options A summary of activity under our equity incentive plans and related information is as follows: Options Outstanding Number of Weighted- Weighted- Aggregate (in thousands) Balance as of January 31, 2017 56,840,189 $ 7.15 7.0 $ 315,502 Options granted 1,000,000 14.92 Options exercised (8,814,019 ) 2.79 Options cancelled/forfeited (2,666,221 ) 13.91 Balance as of January 31, 2018 46,359,949 $ 7.75 6.3 $ 574,224 Vested and exercisable as of January 31, 2018 28,990,955 $ 5.30 5.7 $ 430,325 The aggregate intrinsic value of options vested and exercisable as of January 31, 2018 is calculated based on the difference between the exercise price and the closing price of $20.14 of our Class A common stock on January 31, 2018 . The aggregate intrinsic value of options exercised for the years ended January 31, 2016 , 2017 and 2018 was $29.5 million , $114.2 million and $104.9 million , respectively. The weighted-average grant date fair value of options granted was $8.38 , $5.57 and $5.57 per share for the years ended January 31, 2016 , 2017 and 2018 , respectively. The total grant date fair value of options vested for the years ended January 31, 2016 , 2017 and 2018 was $35.4 million , $61.8 million and $42.5 million , respectively. As of January 31, 2018 , total unamortized stock-based compensation expense related to our employee stock options was $74.4 million , which is expected to be recognized over a weighted-average period of approximately 2.6 years. During the year ended January 31, 2016 , we granted options to purchase 238,000 shares of common stock, net of cancellations, that vest upon satisfaction of performance and service conditions. For those options that management determined that the performance condition was satisfied, stock-based compensation expense of $2.5 million , $3.3 million and $0.6 million was recognized during the years ended January 31, 2016 , 2017 and 2018 , respectively. As of January 31, 2017 and 2018, there were no outstanding stock options subject to performance vesting conditions. In November 2016, we modified employee stock option awards to purchase 800,000 shares of our common stock. The modification included an immediate acceleration of performance-based options to purchase 360,000 shares of common stock and an acceleration of time-based options to purchase 440,000 shares of common stock contingent on continued employment through January 31, 2017. This modification resulted in stock-based compensation expense of $5.9 million that was recognized during the year ended January 31, 2017. Determination of Fair Value The fair value of stock options granted to employees and to be purchased under ESPP is estimated on the grant date using the Black-Scholes option pricing model. This valuation model for stock-based compensation expense requires us to make assumptions and judgments about the variables used in the calculation including the fair value of the underlying common stock, expected term, the expected volatility of the common stock, a risk-free interest rate and expected dividend yield. We estimate the fair value of employee stock options and ESPP purchase rights using a Black-Scholes option pricing model with the following assumptions: Year Ended January 31, 2016 2017 2018 Employee Stock Options Expected term (in years) 6.0 - 7.4 6.1 6.1 Expected volatility 48% - 52% 44 % 47 % Risk-free interest rate 1.5% - 1.9% 1.3% - 1.5% 1.9 % Dividend rate — — — Fair value of common stock $13.94 - $19.68 $10.37 - $14.52 $12.84 Employee Stock Purchase Plan Expected term (in years) 0.4 - 1.9 0.5 - 2.0 0.5 - 2.0 Expected volatility 49 % 41 % 35% - 39% Risk-free interest rate 0.1% - 0.7% 0.5% - 0.9% 0.9% - 1.4% Dividend rate — — — The assumptions used in the Black-Scholes option pricing model were determined as follows. Fair Value of Common Stock —Prior to our IPO in October 2015, our board of directors considered numerous objective and subjective factors to determine the fair value of our common stock at each grant date, including (i) contemporaneous third-party valuations of common stock; (ii) the prices for our convertible preferred stock sold to outside investors; (iii) the rights and preferences of convertible preferred stock relative to common stock; (iv) the lack of marketability of our common stock; (v) developments in the business; and (vi) the likelihood of achieving a liquidity event, such as an IPO or sale of Pure Storage, given prevailing market conditions. Subsequent to our IPO, we use the market closing price of our Class A common stock as reported on the New York Stock Exchange to determine the fair value of our common stock at each grant date. Expected Term —The expected term represents the period that our stock-based awards are expected to be outstanding. The expected term assumptions were determined based on the vesting terms, exercise terms and contractual lives of the options and ESPP purchase rights. Expected Volatility —Since we have limited trading history of our common stock, the expected volatility was derived from the average historical stock volatilities of several public companies within the same industry that we consider to be comparable to our business over a period equivalent to the expected term of the stock option grants and ESPP purchase rights. Risk-Free Interest Rate —The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant for zero-coupon U.S. Treasury notes with maturities approximately equal to the expected term of the stock option grants and ESPP purchase rights. Dividend Rate —We have never declared or paid any cash dividends and do not plan to pay cash dividends in the foreseeable future, and, therefore, use an expected dividend yield of zero . Restricted Stock Units A summary of the restricted stock unit activity under our 2015 Plan and related information is as follows: Number of Restricted Stock Units Outstanding Weighted-Average Grant Date Fair Value Aggregate Intrinsic Value (in thousands) Unvested balance as of January 31, 2017 8,783,024 $ 13.06 $ 99,863 Granted 15,779,364 12.16 Vested (5,277,679) 12.30 Forfeited (1,602,063) 11.88 Unvested balance of January 31, 2018 17,682,646 $ 12.60 $ 356,117 In March 2017, we granted 750,000 performance stock units (net of 77,000 canceled units) with both performance and service vesting conditions payable in common shares from 0% to 150% of the target number granted, contingent upon the degree to which the performance condition is met. At January 31, 2018, the performance condition was satisfied. Stock-based compensation expense for these performance stock units was $4.2 million for the year ended January 31, 2018 and total unamortized stock-based compensation expense was $3.3 million as of January 31, 2018 , which is expected to be recognized over 2.2 years. In August 2017, we granted 464,744 performance stock units with both performance and service vesting conditions payable in common shares from 0% to 150% of the target number granted, contingent upon the degree to which the performance condition is met. Because the performance condition for these stock units was not established as of January 31, 2018 , there was no grant date from an accounting perspective and no stock-based compensation expense was recognized. Also, no grant date fair value was considered in the calculation of weighted-average grant date fair value in the table above. In March 2018, the performance condition for these performance stock units was established and the grant date fair value of these stock units was $21.13 per share. Stock-based compensation expense will be recognized under the accelerated attribution method over the vesting period through December 2020. In March 2018, we converted 1,375,210 performance stock units and restricted stock units to 1,375,210 shares of restricted stock. The conversion did not change the fair value or vesting conditions and therefore no modification is required. The aggregate fair value of restricted stock units that vested during the year ended January 31, 2018 was $75.5 million . As of January 31, 2018, total unamortized stock-based compensation expense related to outstanding restricted stock units was $187.2 million , which is expected to be recognized over a weighted-average period of approximately 2.6 years. Stock-Based Compensation Expense The following table summarizes the components of stock-based compensation expense recognized in the consolidated statements of operations (in thousands): Year Ended January 31, 2016 2017 2018 Cost of revenue—product $ 276 $ 601 $ 1,630 Cost of revenue—support 2,388 5,639 9,050 Research and development 31,135 63,495 71,229 Sales and marketing 16,966 34,317 47,687 General and administrative 7,460 12,616 21,077 Total stock-based compensation expense $ 58,225 $ 116,668 $ 150,673

Net Loss per Share Attributable

Net Loss per Share Attributable to Common Stockholders	12 Months Ended
	Jan. 31, 2018
Earnings Per Share [Abstract]
Net Loss per Share Attributable to Common Stockholders	Net Loss per Share Attributable to Common Stockholders Basic and diluted net loss per share attributable to common stockholders is presented in conformity with the two-class method required for participating securities. Basic net loss per share attributable to common stockholders is computed by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period, less shares subject to repurchase. The diluted net loss per share attributable to common stockholders is computed by giving effect to all potential dilutive common stock equivalents outstanding for the period. For purposes of this calculation, convertible preferred stock, stock options, unvested restricted stock units, repurchasable shares from early exercised stock options and shares subject to ESPP withholding are considered to be common stock equivalents but have been excluded from the calculation of diluted net loss per share attributable to common stockholders as their effect is anti-dilutive. The rights, including the liquidation and dividend rights, of the holders of our Class A and Class B common stock are identical, except with respect to voting. As the liquidation and dividend rights are identical, the undistributed earnings are allocated on a proportionate basis and the resulting net loss per share attributed to common stockholders will, therefore, be the same for both Class A and Class B common stock on an individual or combined basis. We did not present dilutive net loss per share on an if-converted basis because the impact was not dilutive. The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders (in thousands, except per share data): Year Ended January 31, 2016 2017 2018 Net loss $ (213,752 ) $ (245,066 ) $ (177,602 ) Weighted-average shares used in computing net loss 82,460 194,714 211,609 Net loss per share attributable to common stockholders, basic and diluted $ (2.59 ) $ (1.26 ) $ (0.84 ) The following weighted-average outstanding shares of common stock equivalents were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti-dilutive (in thousands): Year Ended January 31, 2016 2017 2018 Stock options to purchase common stock 61,795 63,984 52,424 Restricted stock units — 5,216 15,496 Employee stock purchase plan 170 1,310 1,544 Early exercised stock options 3,618 2,106 246 Total 65,583 72,616 69,710

Income Taxes

Income Taxes	12 Months Ended
	Jan. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The geographical breakdown of loss before provision for income taxes is as follows (in thousands): Year Ended January 31, 2016 2017 2018 Domestic $ (195,019 ) $ (200,355 ) $ (135,115 ) International (17,164 ) (42,824 ) (38,598 ) Total $ (212,183 ) $ (243,179 ) $ (173,713 ) The components of the provision for income taxes are as follows (in thousands): Year Ended January 31, 2016 2017 2018 Current: State $ 210 $ 389 $ 525 Foreign 2,198 1,806 3,580 Total $ 2,408 $ 2,195 $ 4,105 Deferred: Foreign (839 ) (308 ) (216 ) Provision for income taxes $ 1,569 $ 1,887 $ 3,889 The reconciliation of the federal statutory income tax rate and effective income tax rate is as follows (in thousands): Year Ended January 31, 2016 2017 2018 Tax at federal statutory rate $ (72,142 ) $ (82,682 ) $ (57,144 ) State tax, net of federal benefit 152 276 351 Stock-based compensation expense 10,866 (5,242 ) (9,953 ) Research and development tax credits (3,832 ) (1,570 ) (7,629 ) Foreign rate differential 7,106 15,878 18,667 Change in valuation allowance 58,979 73,863 (48,703 ) Remeasurement of deferred tax assets and liabilities — — 107,029 Other 440 1,364 1,271 Provision for income taxes $ 1,569 $ 1,887 $ 3,889 Deferred income taxes reflect the net effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The significant components of our deferred tax assets and liabilities were as follows (in thousands): January 31, 2017 2018 Deferred tax assets: Net operating loss carryforwards $ 173,942 $ 127,621 Tax credit carryover 15,319 33,105 Accruals and reserves 3,112 1,809 Deferred revenue 53,424 46,570 Stock-based compensation expense 26,401 24,133 Depreciation and amortization 7,302 15,367 Charitable contribution carryforwards 4,345 2,892 Other — 465 Total deferred tax assets 283,845 251,962 Valuation allowance (271,779 ) (240,519 ) Total deferred tax assets, net of valuation allowance 12,066 11,443 Deferred tax liabilities: Deferred commissions (11,222 ) (10,383 ) Total deferred tax liabilities (11,222 ) (10,383 ) Net deferred tax assets $ 844 $ 1,060 The Tax Act was signed into law on December 22, 2017. The new legislation decreases the U.S. corporate federal income tax rate from 35% to 21% effective January 1, 2018. As a result, our U.S. federal and state deferred tax assets and valuation allowance each decreased by approximately $98 million , and accordingly there is no impact to our provision for income taxes. Since we have a January 31 fiscal year end, we have a federal blended tax rate of 32.9% for the year ended January 31, 2018 and 21% thereafter on any current U.S. federal taxes payable. The Tax Act also includes a number of other provisions including the elimination of loss carrybacks and limitations on the use of future losses, limitations on the deductibility of executive compensation, limitation or modification on the deductibility of certain business expenses, the transition of U.S. international taxation from a worldwide tax system to a territorial system, and the introduction of a base erosion and anti-abuse tax. We will continue to assess the impact of the Tax Act during the one-year measurement period from the Tax Act enactment date as allowed by Staff Accounting Bulletin No. 118 (SAB 118) issued in connection with the Tax Act. We expect to complete the accounting for the tax effects of the Tax Act in calendar year 2018. As of January 31, 2018 , the undistributed earnings of $20.8 million from non-U.S. operations held by our foreign subsidiaries are designated as permanently reinvested outside the U.S. Accordingly, no additional U.S. income taxes or additional foreign withholding taxes have been provided thereon. Determination of the amount of unrecognized deferred tax liability related to these earnings is not practicable. As of January 31, 2018 , we had net operating loss carryforwards for federal income tax purposes of approximately $508.9 million and state income tax purposes of approximately $331.9 million . These net operating loss carryforwards will expire, if not utilized, beginning in 2028 for federal and state income tax purposes. We had federal and state research and development tax credit carryforwards of approximately $26.6 million and $22.2 million as of January 31, 2018 . The federal research and development tax credit carryforwards will expire commencing in 2028 , while the state research and development tax credit carryforwards have no expiration date. Realization of deferred tax assets is dependent on future taxable income, the existence and timing of which is uncertain. Based on our history of losses, management has determined that it is more likely than not that the U.S. deferred tax assets will not be realized, and accordingly has placed a full valuation allowance on the net U.S. deferred tax assets. The valuation allowance increased by $68.0 million , $90.9 million , and decreased by $31.3 million , respectively, during the years ended January 31, 2016 , 2017 and 2018 . Utilization of the net operating loss carryforwards and credits may be subject to substantial annual limitation due to the ownership change limitations provided by Section 382 of the Internal Revenue Code of 1986, as amended, and similar state provisions. The annual limitation may result in the expiration of net operating losses and credits before utilization. In February 2018, we completed an analysis through January 2018 to evaluate whether there are any limitations of our net operating loss carryforwards and concluded no limitations currently exist. Uncertain Tax Positions The activity related to the unrecognized tax benefits is as follows (in thousands): Year Ended January 31, 2016 2017 2018 Gross unrecognized tax benefits—beginning balance $ 13,874 $ 15,470 $ 6,375 Decreases related to tax positions taken during (3,969 ) (11,286 ) (24 ) Increases related to tax positions taken during 35 — 619 Increases related to tax positions taken during 5,530 2,191 5,431 Gross unrecognized tax benefits—ending balance $ 15,470 $ 6,375 $ 12,401 As of January 31, 2018 , our gross unrecognized tax benefit was approximately $12.4 million , none of which if recognized, would have an impact on the effective tax rate because it would be offset by the reversal of deferred tax assets which are subject to a full valuation allowance. As of January 31, 2018 , we had no current or cumulative interest and penalties related to uncertain tax positions. It is difficult to predict the final timing and resolution of any particular uncertain tax position. Based on our assessment, including experience and complex judgments about future events, we do not expect that changes in the liability for unrecognized tax benefits during the next twelve months will have a significant impact on our consolidated financial position or results of operations. We file income tax returns in the U.S. federal jurisdiction as well as many U.S. states and foreign jurisdictions. Our fiscal year 2014 federal income tax return examination by the Internal Revenue Service was concluded with no adjustments. The tax returns for fiscal years 2013 and forward remain open to examination by the major jurisdictions in which we are subject to tax. The tax returns for fiscal years outside the normal statutes of limitation remain open to audit by tax authorities due to tax attributes generated in those early years, which have been carried forward and may be audited in subsequent years when utilized.

Segment Information

Segment Information	12 Months Ended
	Jan. 31, 2018
Segment Reporting [Abstract]
Segment Information	Segment Information Our chief operating decision maker is a group which is comprised of our Chief Executive Officer, our Chief Financial Officer, and our President. This group reviews financial information presented on a consolidated basis for purposes of allocating resources and evaluating financial performance. We have one business activity and there are no segment managers who are held accountable for operations or operating results. Accordingly, we have a single reportable segment. The following table sets forth revenue by geographic area based on the billing address of our customers (in thousands): Year Ended January 31, 2016 2017 2018 United States $ 343,625 $ 561,352 $ 762,391 Rest of the world 96,708 166,625 260,628 Total revenue $ 440,333 $ 727,977 $ 1,023,019 Long-lived assets by geographic area are summarized as follows (in thousands): January 31, 2017 2018 United States $ 78,692 $ 85,430 Rest of the world 3,003 3,712 Total long-lived assets $ 81,695 $ 89,142

401(k) Plan

401(k) Plan	12 Months Ended
	Jan. 31, 2018
Compensation Related Costs [Abstract]
401(k) Plan	401(k) Plan We have a 401(k) savings plan (the 401(k) plan) which qualifies as a deferred salary arrangement under section 401(k) of the Internal Revenue Code. Under the 401(k) plan, participating employees may elect to contribute up to 100% of their eligible compensation, subject to certain limitations. We have not made any matching contributions to date.

Basis of Presentation and Sum20

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Jan. 31, 2018
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of the company and our wholly owned subsidiaries and have been prepared in conformity with accounting principles generally accepted in the United States (U.S. GAAP). All intercompany balances and transactions have been eliminated in consolidation.
Foreign Currency	Foreign Currency The functional currency of our foreign subsidiaries is the U.S. dollar. Transactions denominated in currencies other than the functional currency are remeasured to the functional currency at the average exchange rate in effect during the period. At the end of each reporting period, monetary assets and liabilities are remeasured using exchange rates in effect at the balance sheet date. Non-monetary assets and liabilities are remeasured at historical exchange rates. Foreign currency transaction gains and losses are recorded in other income (expense), net in the consolidated statements of operations.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported and disclosed in the financial statements and accompanying notes. Actual results could differ from these estimates. Such estimates include, but are not limited to, the determination of best estimate of selling price included in multiple-deliverable revenue arrangements, sales commissions, useful lives of intangible assets and property and equipment, fair values of stock-based awards, provision for income taxes, including related reserves, and contingent liabilities, among others. Management bases its estimates on historical experience and on various other assumptions which management believes to be reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities.
Concentration Risk	Concentration Risk Financial instruments that are exposed to concentration of credit risk consist primarily of cash and cash equivalents and accounts receivable. As of January 31, 2017 and 2018 , substantially all of our cash and cash equivalents have been invested with three financial institutions and such deposits exceed federally insured limits. Management believes that the financial institutions that hold our investments are financially sound and, accordingly, are subject to minimal credit risk. We define a customer as an end user that purchases our products and services from one of our channel partners or from us directly. Our revenue and accounts receivable are derived substantially from the United States across a multitude of industries. We perform ongoing evaluations to determine customer credit. As of January 31, 2017 , we had one channel partner that represented 10% or more of total accounts receivable on that date. As of January 31, 2018 , no channel partner represented 10% or more of total accounts receivable on that date. No single channel partner represented 10% or more of revenue for the years ended January 31, 2016 and 2018. One channel partner represented 11% of revenue for the year ended January 31, 2017. No end customer represented 10% or more of revenue for the years ended January 31, 2016 , 2017 and 2018 . We rely on a limited number of suppliers for our contract manufacturing and certain raw material components. In instances where suppliers fail to perform their obligations, we may be unable to find alternative suppliers or satisfactorily deliver our products to our customers on time.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist of cash in banks and highly liquid investments, primarily money market accounts, purchased with an original maturity of three months or less.
Marketable Securities	Marketable Securities We classify our marketable securities as available-for-sale at the time of purchase and reevaluate such classification at each balance sheet date. We may sell these securities at any time for use in current operations even if they have not yet reached maturity. As a result, we classify our securities, including those with maturities beyond twelve months, as current assets in the consolidated balance sheets. We carry these securities at fair value and record unrealized gains and losses in other comprehensive income (loss), which is reflected as a component of stockholders' equity. We evaluate our securities to assess whether those with unrealized loss positions are other than temporarily impaired. We consider impairments to be other than temporary if they are related to deterioration in credit risk or if it is likely we will sell the securities before the recovery of their cost basis. Realized gains and losses from the sale of marketable securities and declines in value deemed to be other than temporary are determined based on the specific identification method. Realized gains and losses are reported in other income (expense), net in the consolidated statements of operations.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying value of our financial instruments, including cash equivalents, accounts receivable, accounts payable and accrued liabilities, approximates fair value.
Accounts Receivable and Allowance	Accounts Receivable and Allowance Accounts receivable are recorded at the invoiced amount, and stated at realizable value, net of an allowance for doubtful accounts. Credit is extended to customers based on an evaluation of their financial condition and other factors. We generally do not require collateral or other security to support accounts receivable. We perform ongoing credit evaluations of our customers and maintain an allowance for doubtful accounts. We assess the collectability of the accounts by taking into consideration the aging of our trade receivables, historical experience, and management judgment. We write off trade receivables against the allowance when management determines a balance is uncollectible and no longer actively pursues collection of the receivable.
Restricted Cash	Restricted Cash Restricted cash is comprised of cash collateral for letters of credit related to our leases and for a vendor credit card program.
Inventory	Inventory Inventory consists of finished goods and component parts, which are purchased from contract manufacturers. Product demonstration units, which we regularly sell, are the primary component of our inventories. Inventories are stated at the lower of cost or net realizable value. Cost is determined using the specific identification method for finished goods and weighted-average method for component parts. We account for excess and obsolete inventory by reducing the carrying value to the estimated net realizable value of the inventory based upon management’s assumptions about future demand and market conditions. In addition, we record a liability for firm, non-cancelable and unconditional purchase commitments with contract manufacturers and suppliers for quantities in excess of future demand forecasts consistent with excess and obsolete inventory valuations.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization is computed using the straight-line method over the estimated useful lives of the respective assets (test equipment— 2 years , computer equipment and software— 2 to 3 years , furniture and fixtures— 7 years ). Leasehold improvements are amortized over the shorter of their estimated useful lives or the remaining lease term . Depreciation commences once the asset is placed in service.
Intangible Assets	Intangible Assets Intangible assets are stated at cost, net of accumulated amortization. We amortize our intangible assets on a straight-line basis over an estimated useful life of five to seven years. During the year ended January 31, 2017, we acquired certain technology patents for $1.0 million , which are amortized on a straight-line basis over an estimated useful life of five years.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets We review our long-lived assets, including property and equipment, and finite-lived intangible assets for impairment whenever events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. We measure the recoverability of these assets by comparing the carrying amounts to the future undiscounted cash flows the assets are expected to generate. If the total of the future undiscounted cash flows is less than the carrying amount of an asset, we record an impairment charge for the amount by which the carrying amount of the asset exceeds its fair market value.
Deferred Commissions	Deferred Commissions Deferred commissions consist of direct and incremental costs paid to our sales force related to customer contracts. The deferred commission amounts are recoverable through the revenue streams that will be recognized under the related customer contracts. Direct sales commissions are deferred when earned and amortized over the same period that revenue is recognized from the related customer contract. Amortization of deferred commissions is included in sales and marketing expense in the consolidated statements of operations.
Revenue Recognition	Revenue Recognition We derive revenue from two sources: (1) product revenue which includes hardware and embedded software and (2) support revenue which includes customer support, hardware maintenance and software upgrades on a when-and-if-available basis. We recognize revenue when: • Persuasive evidence of an arrangement exists —We rely upon sales agreements and/or purchase orders to determine the existence of an arrangement. • Delivery has occurred —We typically recognize product revenue upon shipment, as title and risk of loss are transferred to our channel partners at that time. Products are typically shipped directly by us to customers, and our channel partners do not stock our inventory. • The fee is fixed or determinable —We assess whether the fee is fixed or determinable based on the payment terms associated with the transaction. • Collection is reasonably assured —We assess collectability based on credit analysis and payment history. Our product revenue is derived from the sale of hardware and operating system software that is integrated into the hardware and therefore deemed essential to its functionality. The hardware and the operating system software essential to the functionality of the hardware are considered non-software deliverables and, therefore, are not subject to industry-specific software revenue recognition guidance. Support revenue is derived from the sale of maintenance and support agreements. Maintenance and support agreements include the right to receive unspecified software upgrades and enhancements on a when-and-if-available basis, bug fixes, parts replacement services related to the hardware, as well as access to our cloud-based management and support platform. Revenue related to maintenance and support agreements are recognized ratably over the contractual term, which generally range from one to five years. Costs related to maintenance and support agreements are expensed as incurred. In addition, our Evergreen Storage program provides our customers who continually maintain active maintenance and support for three years with an included controller refresh with each additional three year maintenance and support renewal. In accordance with multiple-element arrangement accounting guidance, the controller refresh represents an additional deliverable that is a separate unit of accounting and the allocated revenue is recognized in the period in which these controllers are shipped. Most of our arrangements, other than stand-alone renewals of maintenance and support agreements, are multiple-element arrangements with a combination of product and support related deliverables (as defined above). Under multiple-element arrangements, we allocate consideration at the inception of an arrangement to all deliverables based on the relative selling price method in accordance with the hierarchy provided by the multiple-element arrangement accounting guidance, which includes (i) vendor-specific objective evidence (VSOE), of selling price, if available; (ii) third-party evidence (TPE), of selling price, if VSOE is not available; and (iii) best estimate of selling price (BESP), if neither VSOE nor TPE is available. We allocate consideration to support related deliverables based on VSOE and to all other deliverables based on BESP as TPE typically cannot be obtained. • VSOE —We determine VSOE based on our historical pricing and discounting practices for the specific products and services when sold separately. In determining VSOE, we require that a substantial majority of the stand-alone selling prices fall within a reasonably narrow pricing range. • TPE —When VSOE cannot be established for deliverables in multiple-element arrangements, we apply judgment with respect to whether we can establish a selling price based on TPE. TPE is determined based on competitor prices for interchangeable products or services when sold separately to similarly situated customers. However, because our products contain a significant element of proprietary technology and our solutions offer substantially different features and functionality, the comparable pricing of products with similar functionality typically cannot be obtained. • BESP —When neither VSOE nor TPE can be established, we utilize BESP to allocate consideration to deliverables in a multiple-element arrangement. Our process to determine BESP for products and support is based on qualitative and quantitative considerations of multiple factors, which primarily include historical sales, margin objectives and discount behavior. Additional considerations are given to other factors such as customer demographics, costs to manufacture products or provide support, pricing practices and market conditions.
Deferred Revenue	Deferred Revenue Deferred revenue primarily consists of amounts that have been invoiced but that have not yet been recognized as revenue and primarily consists of support. The current portion of deferred revenue represents the amounts that are expected to be recognized as revenue within one year of the consolidated balance sheet date.
Warranty Costs	Warranty Costs We generally provide a three -year warranty on hardware and a 90 -day warranty on our software embedded in the hardware. Our hardware warranty provides for parts replacement for defective components and our software warranty provides for bug fixes. Our maintenance and support agreement provides for the same parts replacement that customers are entitled to under our warranty program, except that replacement parts are delivered according to targeted response times to minimize disruption to our customers’ critical business applications. Substantially all customers purchase maintenance and support agreements. Therefore, given that substantially all our products sales are sold together with maintenance and support agreements, we generally do not have exposure related to warranty costs and no warranty reserve has been recorded.
Research and Development	Research and Development Research and development costs are expensed as incurred. Research and development costs consist primarily of personnel costs including stock-based compensation expense, expensed prototype, to the extent there is no alternative use for that equipment, consulting services, depreciation of equipment used in research and development and allocated overhead costs.
Software Development Costs	Software Development Costs We expense software development costs before technological feasibility is reached. We have determined that technological feasibility is reached shortly before the release of our products and as a result, the development costs incurred after the establishment of technological feasibility and before the release of those products have not been significant and accordingly, all software development costs have been expensed as incurred. Software development costs also include costs incurred related to our hosted applications used to deliver our support services. Capitalization begins when the preliminary project stage is complete, management with the relevant authority authorizes and commits to the funding of the software project, and it is probable the project will be completed and the software will be used to perform the intended function.
Advertising Expenses	Advertising Expenses Advertising costs are expensed as incurred.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation includes expenses related to restricted stock units (RSUs), stock options and purchase rights issued to employees under our ESPP. We determine the fair value of our stock options under our equity plans and purchase rights issued to employees under our ESPP on the date of grant utilizing the Black-Scholes option pricing model, which is impacted by the fair value of our common stock, as well as changes in assumptions regarding a number of subjective variables. These variables include the expected common stock price volatility over the term of the awards, the expected term of the awards, risk-free interest rates and expected dividend yield. RSUs are measured at the fair market value of the underlying stock at the grant date. We recognize stock-based compensation expense for stock-based awards on a straight-line basis over the period during which an employee is required to provide services in exchange for the award (generally the vesting period of the award). Subsequent to the adoption of Accounting Standards Update (ASU) No. 2016-09 (ASU 2016-09) on February 1, 2016, we account for forfeitures as they occur. For stock-based awards granted to employees with a performance condition, we recognize stock-based compensation expense for these awards under the accelerated attribution method over the requisite service period when management determines it is probable that the performance condition will be satisfied.
Income Taxes	Income Taxes We account for income taxes using the asset and liability method. Deferred income taxes are recognized by applying enacted statutory tax rates applicable to future years to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. The measurement of deferred tax assets is reduced, if necessary, by a valuation allowance to amounts that are more likely than not to be realized. We recognize tax benefits from uncertain tax positions only if we believe that it is more likely than not that the tax position will be sustained on examination by the taxing authorities based on the technical merits of the position. The tax benefits recognized in the financial statements from such positions are then measured based on the largest benefit that has a greater than 50% likelihood of being realized upon settlement.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (ASU 2014-09 or ASC 606), requiring an entity to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those goods or services. ASC 606 will supersede nearly all existing revenue recognition guidance under U.S. GAAP when it becomes effective. The standard permits two methods of adoptions: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of applying the standard recognized at the date of application (cumulative catch-up transition method). We have adopted the standard using the full retrospective method beginning February 1, 2018, for the year ending January 31, 2019, and our historical financial information for the years ended January 31, 2017 and 2018 will be restated to conform to the new standard. The impact on our consolidated financial statements upon the adoption of the standard is primarily as follows: • An increase in total revenue of $11.2 million and $1.8 million for the years ended January 31, 2017 and 2018 (an increase in product revenue of $24.5 million and $20.5 million for the years ended January 31, 2017 and 2018 and a decrease in support revenue of $13.3 million and $18.7 million for the years ended January 31, 2017 and 2018), and a decrease in deferred revenue of $30.1 million and $31.9 million as of January 31, 2017 and 2018, due to the removal of limitation on contingent revenue; • A decrease in commission expense of $12.3 million and $16.0 million for the years ended January 31, 2017 and 2018, and an increase in deferred commissions of $28.2 million and $44.2 million as of January 31, 2017 and 2018, due to a change in amortization period from contract term (typically ranging from one to five years) to an expected useful life of six years; • A decrease in loss from operations of $23.5 million and $17.8 million for the years ended January 31, 2017 and 2018, due to the changes above. In addition, the adoption of the standard does not have a significant impact to the provision for income taxes on our consolidated statements of operations, nor does it impact net cash provided by or used in operating, investing, or financing activities on our consolidated statements of cash flows. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (ASU 2016-02). ASU 2016-02 requires lessees to recognize all leases with terms in excess of one year on their balance sheet as a right-of-use asset and a lease liability at the commencement date. The new standard also simplifies the accounting for sale and leaseback transactions. The amendments in this update will be effective for us beginning on February 1, 2019 and must be adopted using a modified retrospective method for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. Early adoption is permitted. We are currently evaluating adoption methods and the impact of this standard on our consolidated financial statements. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13). ASU 2016-13 amends guidance on reporting credit losses for assets held at amortized cost basis and available-for-sale debt securities to require that credit losses on available-for-sale debt securities be presented as an allowance rather than as a write-down. The measurement of credit losses for newly recognized financial assets and subsequent changes in the allowance for credit losses are recorded in the statements of operations. The amendments in this update will be effective for us beginning on February 1, 2020 with early adoption permitted on or after February 1, 2019. We are currently evaluating the impact of this standard on our consolidated financial statements. In August 2016, the FASB issued ASU No. 2016-15 (Topic 230) Statement of Cash Flow: Classification of Certain Cash Receipts and Cash Payments, which clarifies how companies present and classify certain cash receipts and cash payments in the statement of cash flows. This standard is effective for us beginning on February 1, 2018 and will be applied on a retrospective basis. We do not expect the adoption of this standard will have a significant impact on our consolidated financial statements. In October 2016, the FASB issued ASU No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory (ASU 2016-16), which requires the recognition of the income tax consequences of an intra-entity transfer of an asset, other than inventory, when the transfer occurs. ASU 2016-16 will be effective for us beginning on February 1, 2018 and will be applied on a modified retrospective basis. Early adoption is permitted. We do not expect the adoption of this standard will have a material impact our consolidated financial statements. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (ASU 2016-18), which requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. ASU 2016-18 will be effective for us beginning on February 1, 2018 and will be applied on a retrospective basis. We do not expect the adoption of this standard will have a significant impact on our cash flow activity presented on our consolidated statements of cash flows. In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718)-Scope of Modification Accounting, to clarify when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new standard, modification is required only if the fair value, the vesting conditions, or the classification of an award as equity or liability changes as a result of the change in terms or conditions. This standard will be effective for us beginning February 1, 2018 and will be applied on a prospective basis. We do not expect the adoption of this standard will have a significant impact on our consolidated financial statements. In February 2018, the FASB issued ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220) - Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. This standard allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act and requires certain disclosures about stranded tax effects. This standard will be effective for us beginning February 1, 2019 and should be applied either in the period of adoption or retrospectively. Early adoption is permitted. We are currently evaluating the impact of this standard on our consolidated financial statements. In March 2018, the FASB issued ASU No. 2018-05, Income Taxes (Topic 740) - Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118 ("ASU 2018-05"). This standard amends Accounting Standards Codification 740, Income Taxes (ASC 740) to provide guidance on accounting for the tax effects of the Tax Cuts and Jobs Act (the Tax Act) pursuant to Staff Accounting Bulletin No. 18, which allows companies to complete the accounting under ASC 740 within a one-year measurement period from the Tax Act enactment date. This standard is effective upon issuance. We are currently evaluating the impact of this standard on our consolidated financial statements
Reclassifications	Reclassifications Certain amounts in prior periods have been reclassified to conform with current period presentation.

Basis of Presentation and Sum21

Basis of Presentation and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Jan. 31, 2018
Accounting Policies [Abstract]
Schedule of Changes in Allowance for Doubtful Accounts	The following table presents the changes in the allowance for doubtful accounts: Year Ended January 31, 2016 2017 2018 (in thousands) Allowance for doubtful accounts, beginning balance $ 210 $ 944 $ 2,000 Provision, net 918 1,394 482 Writeoffs (184 ) (338 ) (1,420 ) Allowance for doubtful accounts, ending balance $ 944 $ 2,000 $ 1,062

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Jan. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value, Assets Measured on Recurring Basis	The following tables summarize our cash equivalents, marketable securities and restricted cash by significant investment categories as of January 31, 2017 and 2018 (in thousands): January 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Cash Equivalents Marketable Securities Restricted Cash Level 1 Money market accounts $ — $ — $ — $ 12,734 $ — $ — $ 12,734 Level 2 U.S. government treasury notes 148,298 22 (289 ) 148,031 13,226 134,805 — U.S. government agencies 40,398 2 (159 ) 40,241 — 40,241 — Corporate debt securities 185,701 242 (379 ) 185,564 — 185,564 — Foreign government bonds 2,377 2 (3 ) 2,376 — 2,376 — Total $ 376,774 $ 268 $ (830 ) $ 388,946 $ 13,226 $ 362,986 $ 12,734 January 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Cash Equivalents Marketable Securities Restricted Cash Level 1 Money market accounts $ — $ — $ — $ 32,057 $ 17,294 $ — $ 14,763 Level 2 U.S. government treasury notes 131,643 — (651 ) 130,992 10,172 120,820 — U.S. government agencies 47,229 — (333 ) 46,896 — 46,896 — Corporate debt securities 186,506 116 (1,049 ) 185,573 — 185,573 — Total $ 365,378 $ 116 $ (2,033 ) $ 395,518 $ 27,466 $ 353,289 $ 14,763
Investments Classified by Contractual Maturity Date	The amortized cost and estimated fair value of our marketable securities are shown below by contractual maturity (in thousands): January 31, 2018 Amortized Cost Fair Value Due within one year $ 173,537 $ 173,278 Due in one to five years 181,669 180,011 Total $ 355,206 $ 353,289
Schedule of Unrealized Loss on Investments	The following table presents gross unrealized losses and fair values for those investments that were in a continuous unrealized loss position as of January 31, 2018 , aggregated by investment category (in thousands): Less than 12 months Greater than 12 months Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss U.S. government treasury notes $ 68,212 $ (219 ) $ 52,607 $ (432 ) $ 120,819 $ (651 ) U.S. government agencies 23,004 (156 ) 23,892 (177 ) 46,896 (333 ) Corporate debt securities 117,165 (732 ) 33,132 (317 ) 150,297 (1,049 ) Total $ 208,381 $ (1,107 ) $ 109,631 $ (926 ) $ 318,012 $ (2,033 )

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Jan. 31, 2018
Balance Sheet Components Disclosure [Abstract]
Schedule of Inventory, Current	Inventory consists of the following (in thousands): January 31, 2017 2018 Raw materials $ 3,003 $ 1,181 Finished goods 20,495 33,316 Inventory $ 23,498 $ 34,497
Schedule of Property and Equipment, Net	Property and equipment, net consists of the following (in thousands): January 31, 2017 2018 Test equipment $ 105,955 $ 142,311 Computer equipment and software 54,521 72,329 Furniture and fixtures 4,494 5,363 Leasehold improvements 10,332 15,032 Total property and equipment 175,302 235,035 Less: accumulated depreciation and amortization (93,607 ) (145,893 ) Property and equipment, net $ 81,695 $ 89,142
Schedule of Intangible Assets, Net	Intangible assets, net consist of the following (in thousands): January 31, 2017 2018 Technology patents $ 10,125 $ 10,125 Accumulated amortization (3,565 ) (5,068 ) Intangible assets, net $ 6,560 $ 5,057
Schedule of Expected Amortization Expenses for Intangible Assets	As of January 31, 2018 , expected future amortization expense for intangible assets is as follows (in thousands): Year Ending January 31, Estimated Future 2019 $ 1,504 2020 1,504 2021 1,504 2022 545 Total $ 5,057
Schedule of Accrued Expenses and Other Liabilities	Accrued expenses and other liabilities consist of the following (in thousands): January 31, 2017 2018 Taxes payable $ 1,675 $ 4,052 Accrued marketing 6,718 5,928 Accrued travel and entertainment expenses 2,235 4,386 Other accrued liabilities 11,069 12,463 Total accrued expenses and other liabilities $ 21,697 $ 26,829

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Jan. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule Aggregate Future Minimum Payments Under Non-Cancelable Operating Leases	As of January 31, 2018 , the aggregate future minimum payments under non-cancelable operating leases consist of the following (in thousands): Year Ending January 31, Operating Leases 2019 $ 19,321 2020 18,627 2021 20,083 2022 17,250 2023 13,991 Thereafter 23,727 Total $ 112,999

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Jan. 31, 2018
Equity [Abstract]
Summary of Reserved Shares of Common Stock for Future Issuance	As of January 31, 2018 , we had reserved shares of common stock for future issuance as follows: January 31, 2018 Shares underlying outstanding stock options 46,359,949 Shares underlying outstanding restricted stock units 17,682,646 Shares reserved for future equity awards 19,684,916 Shares reserved for future employee stock purchase plan awards 2,489,767 Total 86,217,278

Equity Incentive Plans (Tables)

Equity Incentive Plans (Tables)	12 Months Ended
	Jan. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock Option Activity Under Equity Incentive Plans and Related Information	A summary of activity under our equity incentive plans and related information is as follows: Options Outstanding Number of Weighted- Weighted- Aggregate (in thousands) Balance as of January 31, 2017 56,840,189 $ 7.15 7.0 $ 315,502 Options granted 1,000,000 14.92 Options exercised (8,814,019 ) 2.79 Options cancelled/forfeited (2,666,221 ) 13.91 Balance as of January 31, 2018 46,359,949 $ 7.75 6.3 $ 574,224 Vested and exercisable as of January 31, 2018 28,990,955 $ 5.30 5.7 $ 430,325
Summary of Estimate Fair Value of Employee Stock Options and Employee Purchase Plan	We estimate the fair value of employee stock options and ESPP purchase rights using a Black-Scholes option pricing model with the following assumptions: Year Ended January 31, 2016 2017 2018 Employee Stock Options Expected term (in years) 6.0 - 7.4 6.1 6.1 Expected volatility 48% - 52% 44 % 47 % Risk-free interest rate 1.5% - 1.9% 1.3% - 1.5% 1.9 % Dividend rate — — — Fair value of common stock $13.94 - $19.68 $10.37 - $14.52 $12.84 Employee Stock Purchase Plan Expected term (in years) 0.4 - 1.9 0.5 - 2.0 0.5 - 2.0 Expected volatility 49 % 41 % 35% - 39% Risk-free interest rate 0.1% - 0.7% 0.5% - 0.9% 0.9% - 1.4% Dividend rate — — —
Schedule of Share-based Compensation, Restricted Stock Units Award Activity	A summary of the restricted stock unit activity under our 2015 Plan and related information is as follows: Number of Restricted Stock Units Outstanding Weighted-Average Grant Date Fair Value Aggregate Intrinsic Value (in thousands) Unvested balance as of January 31, 2017 8,783,024 $ 13.06 $ 99,863 Granted 15,779,364 12.16 Vested (5,277,679) 12.30 Forfeited (1,602,063) 11.88 Unvested balance of January 31, 2018 17,682,646 $ 12.60 $ 356,117
Summarizes the Components of Stock-Based Compensation	The following table summarizes the components of stock-based compensation expense recognized in the consolidated statements of operations (in thousands): Year Ended January 31, 2016 2017 2018 Cost of revenue—product $ 276 $ 601 $ 1,630 Cost of revenue—support 2,388 5,639 9,050 Research and development 31,135 63,495 71,229 Sales and marketing 16,966 34,317 47,687 General and administrative 7,460 12,616 21,077 Total stock-based compensation expense $ 58,225 $ 116,668 $ 150,673

Net Loss per Share Attributab27

Net Loss per Share Attributable to Common Stockholders (Tables)	12 Months Ended
	Jan. 31, 2018
Earnings Per Share [Abstract]
Summary of Computation of Basic and Diluted Net Loss per Share Attributable to Common Stockholders	The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders (in thousands, except per share data): Year Ended January 31, 2016 2017 2018 Net loss $ (213,752 ) $ (245,066 ) $ (177,602 ) Weighted-average shares used in computing net loss 82,460 194,714 211,609 Net loss per share attributable to common stockholders, basic and diluted $ (2.59 ) $ (1.26 ) $ (0.84 )
Summary of Weighted-average Outstanding Shares Excluded from Computation of Diluted Net Loss per Share Attributable to Common Stockholders	The following weighted-average outstanding shares of common stock equivalents were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti-dilutive (in thousands): Year Ended January 31, 2016 2017 2018 Stock options to purchase common stock 61,795 63,984 52,424 Restricted stock units — 5,216 15,496 Employee stock purchase plan 170 1,310 1,544 Early exercised stock options 3,618 2,106 246 Total 65,583 72,616 69,710

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Jan. 31, 2018
Income Tax Disclosure [Abstract]
Schedule Of Geographical Breakdown Of Loss Before Provision For Income Taxes	The geographical breakdown of loss before provision for income taxes is as follows (in thousands): Year Ended January 31, 2016 2017 2018 Domestic $ (195,019 ) $ (200,355 ) $ (135,115 ) International (17,164 ) (42,824 ) (38,598 ) Total $ (212,183 ) $ (243,179 ) $ (173,713 )
Schedule of Components of Provision for Income Taxes	The components of the provision for income taxes are as follows (in thousands): Year Ended January 31, 2016 2017 2018 Current: State $ 210 $ 389 $ 525 Foreign 2,198 1,806 3,580 Total $ 2,408 $ 2,195 $ 4,105 Deferred: Foreign (839 ) (308 ) (216 ) Provision for income taxes $ 1,569 $ 1,887 $ 3,889
Reconciliation of the Federal Statutory Income Tax Rate and Effective Income Tax Rate	The reconciliation of the federal statutory income tax rate and effective income tax rate is as follows (in thousands): Year Ended January 31, 2016 2017 2018 Tax at federal statutory rate $ (72,142 ) $ (82,682 ) $ (57,144 ) State tax, net of federal benefit 152 276 351 Stock-based compensation expense 10,866 (5,242 ) (9,953 ) Research and development tax credits (3,832 ) (1,570 ) (7,629 ) Foreign rate differential 7,106 15,878 18,667 Change in valuation allowance 58,979 73,863 (48,703 ) Remeasurement of deferred tax assets and liabilities — — 107,029 Other 440 1,364 1,271 Provision for income taxes $ 1,569 $ 1,887 $ 3,889
Significant Components of Deferred Tax Assets and Liabilities	The significant components of our deferred tax assets and liabilities were as follows (in thousands): January 31, 2017 2018 Deferred tax assets: Net operating loss carryforwards $ 173,942 $ 127,621 Tax credit carryover 15,319 33,105 Accruals and reserves 3,112 1,809 Deferred revenue 53,424 46,570 Stock-based compensation expense 26,401 24,133 Depreciation and amortization 7,302 15,367 Charitable contribution carryforwards 4,345 2,892 Other — 465 Total deferred tax assets 283,845 251,962 Valuation allowance (271,779 ) (240,519 ) Total deferred tax assets, net of valuation allowance 12,066 11,443 Deferred tax liabilities: Deferred commissions (11,222 ) (10,383 ) Total deferred tax liabilities (11,222 ) (10,383 ) Net deferred tax assets $ 844 $ 1,060
Summary of Activity Related to Unrecognized Tax Benefits	The activity related to the unrecognized tax benefits is as follows (in thousands): Year Ended January 31, 2016 2017 2018 Gross unrecognized tax benefits—beginning balance $ 13,874 $ 15,470 $ 6,375 Decreases related to tax positions taken during (3,969 ) (11,286 ) (24 ) Increases related to tax positions taken during 35 — 619 Increases related to tax positions taken during 5,530 2,191 5,431 Gross unrecognized tax benefits—ending balance $ 15,470 $ 6,375 $ 12,401

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Jan. 31, 2018
Segment Reporting [Abstract]
Schedule of Revenue by Geographic Area	The following table sets forth revenue by geographic area based on the billing address of our customers (in thousands): Year Ended January 31, 2016 2017 2018 United States $ 343,625 $ 561,352 $ 762,391 Rest of the world 96,708 166,625 260,628 Total revenue $ 440,333 $ 727,977 $ 1,023,019
Schedule of Long-Lived Assets by Geographic Area	Long-lived assets by geographic area are summarized as follows (in thousands): January 31, 2017 2018 United States $ 78,692 $ 85,430 Rest of the world 3,003 3,712 Total long-lived assets $ 81,695 $ 89,142

Business Overview - Additional

Business Overview - Additional Information (Details) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Oct. 31, 2015USD ($)$ / sharesshares	Jan. 31, 2018USD ($)class	Jan. 31, 2017USD ($)	Jan. 31, 2016USD ($)
Class of Stock [Line Items]
Net proceeds from initial public offering		$ 0	$ 0	$ 459,425
Number of classes of stock | class		2
IPO
Class of Stock [Line Items]
Net proceeds from initial public offering	$ 459,400
Underwriting discounts and commissions	29,300
Offering costs incurred	$ 4,500
IPO | Class A common stock
Class of Stock [Line Items]
Issuance of common stock upon initial public offering (in shares) | shares	28,750,000
Issue price per share (in dollars per share) | $ / shares	$ 17
IPO | Class B common stock
Class of Stock [Line Items]
Conversion of preferred stock (in shares) | shares	122,280,679

Basis of Presentation and Sum31

Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Concentration Risk [Line Items]
Net foreign currency transaction gains (losses)	$ 6,000,000	$ (2,600,000)	$ (2,300,000)
Restricted cash	14,763,000	12,734,000
Acquisition of intangible assets	0	1,000,000	0
Impairment charges	0	0	0
Deferred commissions, current	22,437,000	15,787,000
Deferred income taxes, non-current	20,300,000	14,900,000
Sales commission expenses	$ 119,800,000	84,800,000	47,200,000
Period required with included controller refresh to have additional maintenance and support renewal	3 years
Additional maintenance and support period	3 years
Warranty reserve	$ 0
Capitalization of software development cost	0	0	0
Advertising expenses	$ 10,300,000	$ 10,700,000	$ 6,200,000
Hardware
Concentration Risk [Line Items]
Standard product warranty period	3 years
Embedded Software
Concentration Risk [Line Items]
Standard product warranty period	90 days
Technology patents
Concentration Risk [Line Items]
Acquisition of intangible assets	$ 1,000,000
Minimum
Concentration Risk [Line Items]
Contractual term	1 year
Minimum | Technology patents
Concentration Risk [Line Items]
Estimated useful life of intangible assets	5 years
Maximum
Concentration Risk [Line Items]
Contractual term	5 years
Maximum | Technology patents
Concentration Risk [Line Items]
Estimated useful life of intangible assets			7 years
Test equipment
Concentration Risk [Line Items]
Property and equipment, useful life	2 years
Computer equipment and software | Minimum
Concentration Risk [Line Items]
Property and equipment, useful life	2 years
Computer equipment and software | Maximum
Concentration Risk [Line Items]
Property and equipment, useful life	3 years
Furniture and fixtures
Concentration Risk [Line Items]
Property and equipment, useful life	7 years
Customer concentration risk | Sales revenue net
Concentration Risk [Line Items]
Concentration risk percentage		11.00%

Basis of Presentation and Sum32

Basis of Presentation and Summary of Significant Accounting Policies - Schedule of Changes in Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Allowance for Doubtful Accounts Receivable [Roll Forward]
Allowance for doubtful accounts, beginning balance	$ 2,000	$ 944	$ 210
Provision, net	482	1,394	918
Writeoffs	(1,420)	(338)	(184)
Allowance for doubtful accounts, ending balance	$ 1,062	$ 2,000	$ 944

Basis of Presentation and Sum33

Basis of Presentation and Summary of Significant Accounting Policies - Recently Adopted Accounting Standards (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in revenue	$ 1,023,019	$ 727,977	$ 440,333
Increase in product revenue	813,985	590,001	375,733
Decrease in support revenue	(209,034)	(137,976)	(64,600)
Decrease in loss from operations	$ 185,158	244,806	$ 210,181
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contractual term	1 year
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contractual term	5 years
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in revenue	$ 1,800	11,200
Increase in product revenue	20,500	24,500
Decrease in support revenue	(18,700)	(13,300)
Decrease in deferred revenue	31,900	30,100
Decrease in commission expense	16,000	12,300
Increase in deferred commissions	44,200	28,200
Decrease in loss from operations	$ 17,800	$ 23,500
Accounting Standards Update 2014-09 | Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contractual term	1 year
Accounting Standards Update 2014-09 | Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contractual term	5 years

Financial Instruments - Fair Va

Financial Instruments - Fair Value of Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Jan. 31, 2018	Jan. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	$ 365,378	$ 376,774
Gross Unrealized Gains	116	268
Gross Unrealized Losses	(2,033)	(830)
Fair Value	395,518	388,946
Cash Equivalents	27,466	13,226
Marketable Securities	353,289	362,986
Restricted Cash	14,763	12,734
Money market accounts | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	32,057	12,734
Cash Equivalents	17,294	0
Marketable Securities	0	0
Restricted Cash	14,763	12,734
U.S. government treasury notes | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	131,643	148,298
Gross Unrealized Gains	0	22
Gross Unrealized Losses	(651)	(289)
Fair Value	130,992	148,031
Cash Equivalents	10,172	13,226
Marketable Securities	120,820	134,805
Restricted Cash	0	0
U.S. government agencies | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	47,229	40,398
Gross Unrealized Gains	0	2
Gross Unrealized Losses	(333)	(159)
Fair Value	46,896	40,241
Cash Equivalents	0	0
Marketable Securities	46,896	40,241
Restricted Cash	0	0
Corporate debt securities | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	186,506	185,701
Gross Unrealized Gains	116	242
Gross Unrealized Losses	(1,049)	(379)
Fair Value	185,573	185,564
Cash Equivalents	0	0
Marketable Securities	185,573	185,564
Restricted Cash	$ 0	0
Foreign government bonds | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost		2,377
Gross Unrealized Gains		2
Gross Unrealized Losses		(3)
Fair Value		2,376
Cash Equivalents		0
Marketable Securities		2,376
Restricted Cash		$ 0

Financial Instruments - Schedul

Financial Instruments - Schedule of Amortized Cost and Estimated Fair Value of Marketable Securities by Contractual Maturity (Details) (Details) $ in Thousands	Jan. 31, 2018USD ($)
Fair Value Disclosures [Abstract]
Due within one year, Amortized Cost	$ 173,537
Due in one to five years, Amortized Cost	181,669
Total, Amortized Cost	355,206
Due within one year, Fair Value	173,278
Due in one to five years, Fair Value	180,011
Total, Fair Value	$ 353,289

Financial Instruments - Sched36

Financial Instruments - Schedule of Gross Unrealized Losses and Fair Values for Investments that were in Continuous Unrealized Loss Position for Less Than 12 Months, Aggregated by Investments Category (Details) $ in Thousands	Jan. 31, 2018USD ($)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 208,381
Greater than 12 months	109,631
Total	318,012
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months	(1,107)
Greater than 12 months	(926)
Total	(2,033)
U.S. government treasury notes
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	68,212
Greater than 12 months	52,607
Total	120,819
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months	(219)
Greater than 12 months	(432)
Total	(651)
U.S. government agencies
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	23,004
Greater than 12 months	23,892
Total	46,896
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months	(156)
Greater than 12 months	(177)
Total	(333)
Corporate debt securities
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	117,165
Greater than 12 months	33,132
Total	150,297
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months	(732)
Greater than 12 months	(317)
Total	$ (1,049)

Balance Sheet Components - Inve

Balance Sheet Components - Inventory (Details) - USD ($) $ in Thousands	Jan. 31, 2018	Jan. 31, 2017
Balance Sheet Components [Abstract]
Raw materials	$ 1,181	$ 3,003
Finished goods	33,316	20,495
Inventory	$ 34,497	$ 23,498

Balance Sheet Components - Prop

Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Property Plant And Equipment [Line Items]
Total property and equipment, gross	$ 235,035	$ 175,302
Less: accumulated depreciation and amortization	(145,893)	(93,607)
Property and equipment, net	89,142	81,695
Depreciation and amortization	60,200	48,800	$ 31,000
Test equipment
Property Plant And Equipment [Line Items]
Total property and equipment, gross	142,311	105,955
Computer equipment and software
Property Plant And Equipment [Line Items]
Total property and equipment, gross	72,329	54,521
Furniture and fixtures
Property Plant And Equipment [Line Items]
Total property and equipment, gross	5,363	4,494
Leasehold improvements
Property Plant And Equipment [Line Items]
Total property and equipment, gross	$ 15,032	$ 10,332

Balance Sheet Components - Inta

Balance Sheet Components - Intangible Assets, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Finite Lived Intangible Assets [Line Items]
Intangible assets, net	$ 5,057	$ 6,560
Intangible assets amortization expense	1,500	1,400	$ 1,300
Technology patents
Finite Lived Intangible Assets [Line Items]
Technology patents	10,125	10,125
Accumulated amortization	(5,068)	(3,565)
Intangible assets, net	$ 5,057	$ 6,560
Weighted average remaining useful life	3 years 5 months

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Expected Amortization Expenses for Intangible Assets (Details) - USD ($) $ in Thousands	Jan. 31, 2018	Jan. 31, 2017
Balance Sheet Components Disclosure [Abstract]
2,019	$ 1,504
2,020	1,504
2,021	1,504
2,022	545
Intangible assets, net	$ 5,057	$ 6,560

Balance Sheet Components - Sc41

Balance Sheet Components - Schedule of Accrued Expenses and Other Liabilities (Details) - USD ($) $ in Thousands	Jan. 31, 2018	Jan. 31, 2017
Balance Sheet Components Disclosure [Abstract]
Taxes payable	$ 4,052	$ 1,675
Accrued marketing	5,928	6,718
Accrued travel and entertainment expenses	4,386	2,235
Other accrued liabilities	12,463	11,069
Total accrued expenses and other liabilities	$ 26,829	$ 21,697

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details)	Oct. 18, 2016USD ($)	Mar. 31, 2018USD ($)ft²	Aug. 31, 2017USD ($)ft²	Jan. 31, 2018USD ($)	Jan. 31, 2017USD ($)	Jan. 31, 2016USD ($)
Loss Contingencies [Line Items]
Aggregate future minimum payments under non-cancelable operating leases				$ 112,999,000
Rent expense recognized under operating leases				19,400,000	$ 16,600,000	$ 11,000,000
Non-cancelable purchase obligation related to software services				26,800,000	4,100,000
Outstanding letters of credit				9,600,000	$ 7,700,000
Loss contingency				$ 0
Dell
Loss Contingencies [Line Items]
Loss contingency, damages awarded, value	$ 30,000,000
Mountain View, California
Loss Contingencies [Line Items]
Lessee, operating lease, term of contract			7 years
Lessee, operating lease, area of property (in sqft) | ft²			45,831
Aggregate future minimum payments under non-cancelable operating leases			$ 32,200,000
Mountain View, California | Letter of Credit
Loss Contingencies [Line Items]
Debt instrument, face amount			$ 2,600,000
Mountain View, California | Subsequent Event
Loss Contingencies [Line Items]
Lessee, operating lease, term of contract		10 years
Lessee, operating lease, area of property (in sqft) | ft²		31,571
Aggregate future minimum payments under non-cancelable operating leases		$ 34,800,000
Mountain View, California | Subsequent Event | Letter of Credit
Loss Contingencies [Line Items]
Debt instrument, face amount		$ 1,500,000

Commitments and Contingencies43

Commitments and Contingencies - Aggregate Future Minimum Payments Under Non-Cancelable Operating Leases (Details) $ in Thousands	Jan. 31, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,019	$ 19,321
2,020	18,627
2,021	20,083
2,022	17,250
2,023	13,991
Thereafter	23,727
Aggregate future minimum payments under non-cancelable operating leases	$ 112,999

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Jan. 31, 2018USD ($)voteclass$ / sharesshares	Jan. 31, 2017$ / sharesshares	Oct. 31, 2015shares	Sep. 30, 2015shares
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	20,000,000	20,000,000	20,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Number of classes of stock | class	2
Common stock, shares authorized (in shares)	2,250,000,000	2,250,000,000
Common stock, shares issued (in shares)	220,979,000	204,364,000
Common stock, shares outstanding (in shares)	220,979,000	204,364,000
Convertible stock, automatic conversion, period after founders death	9 months
Convertible stock, automatic conversion, period after IPO	10 years
Class A common stock
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	2,000,000,000	2,000,000,000
Common stock, par value per share (in dollars per share) | $ / shares	$ 0.0001	$ 0.0001
Common stock, shares issued (in shares)	129,502,242	87,027,000
Common stock, shares outstanding (in shares)	129,502,000	87,027,000
Common stock, entitled votes per share (in votes per share) | vote	1
Class B common stock
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	250,000,000	250,000,000
Common stock, par value per share (in dollars per share) | $ / shares	$ 0.0001	$ 0.0001
Common stock, shares issued (in shares)	91,476,735	117,337,000
Common stock, shares outstanding (in shares)	91,477,000	117,337,000
Common stock, entitled votes per share (in votes per share) | vote	10
Convertible stock, automatic conversion, portion of outstanding stock, percentage	10.00%
Class B common stock | Pure Good Foundation
Class of Stock [Line Items]
Common stock, shares issued (in shares)				700,000
Non cash general and administrative expense | $	$ 11.9

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Reserved Shares of Common Stock for Future Issuance (Details) - shares	Jan. 31, 2018	Jan. 31, 2017
Class of Stock [Line Items]
Shares underlying outstanding equity awards (in shares)	46,359,949	56,840,189
Shares reserved for future equity awards (in shares)	86,217,278
Employee stock purchase plan
Class of Stock [Line Items]
Shares reserved for future equity awards (in shares)	2,489,767
Restricted stock units
Class of Stock [Line Items]
Shares reserved for future equity awards (in shares)	17,682,646
Employee Stock Options
Class of Stock [Line Items]
Shares reserved for future equity awards (in shares)	19,684,916

Equity Incentive Plans - Additi

Equity Incentive Plans - Additional Information (Details)	12 Months Ended
	Jan. 31, 2018planshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of equity incentive plans | plan	2
2015 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity awards of vest expire period	10 years
2015 Equity Incentive Plan | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase price as percentage of fair market value of common stock	100.00%
Equity awards of vest period	2 years
2015 Equity Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity awards of vest period	4 years
2015 Equity Incentive Plan | Class A common stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares initially reserved for issuance (in shares) | shares	27,000,000
Increase in shares reserved by percentage of capital stock	5.00%

Equity Incentive Plans - 2015 E

Equity Incentive Plans - 2015 Employee Stock Purchase Plan (Details)	Mar. 16, 2017USD ($)	Mar. 16, 2016USD ($)	Aug. 31, 2015USD ($)periodshares	Jan. 31, 2018USD ($)shares	Jan. 31, 2017USD ($)	Jan. 31, 2016USD ($)	Jan. 31, 2018USD ($)resetshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for future equity awards (in shares) | shares				86,217,278			86,217,278
Stock-based compensation expense				$ 150,673,000	$ 116,668,000	$ 58,225,000
Unrecognized compensation cost related to stock awards, weighted-average period				2 years 7 months 6 days
2015 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Employee stock purchase plan offering period		24 months
Number of purchase periods | period			4
Purchase period, term			6 months
Stock-based compensation expense				$ 18,300,000	$ 18,300,000	$ 4,400,000
Unrecognized stock-based compensation expense				$ 26,400,000			$ 26,400,000
Unrecognized compensation cost related to stock awards, weighted-average period				1 year 1 month 6 days
2015 Employee Stock Purchase Plan | Through March 15, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Employee stock purchase plan offering period		24 months
ESPP modification charge		$ 10,600,000
2015 Employee Stock Purchase Plan | Through March 15, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Employee stock purchase plan offering period		24 months
ESPP modification charge	$ 9,000,000
Class A common stock | 2015 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for future equity awards (in shares) | shares			3,500,000
Increase in shares reserved by percentage of capital stock			1.00%
Payroll deductions percentage			30.00%
Share cap for ESPP at purchase date (in shares) | shares			3,000
Calendar year gap for ESPP contribution amount			$ 25,000
Purchase price as percentage of fair market value of common stock			85.00%
Number of plan resets | reset							2

Equity Incentive Plans - Early

Equity Incentive Plans - Early Exercise of Stock Options (Details) - USD ($)	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of common stock upon exercise of stock options (in shares)	8,814,019
Early Exercise of Stock Options | Employee Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of common stock upon exercise of stock options (in shares)	0	0	0
Unvested stock option, common stock repurchased during the period (in shares)	0	0	15,000
Common stock subject to repurchase (in shares)	85,262	494,117
Common stock subject to repurchase, aggregate price	$ 300,000	$ 1,400,000

Equity Incentive Plans - Summar

Equity Incentive Plans - Summary of Activity Under the Equity Incentive Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017
Options Outstanding, Number of Shares
Balance as of January 31, 2017 (in shares)	56,840,189
Options granted (in shares)	1,000,000
Options exercised (in shares)	(8,814,019)
Options cancelled/forfeited (in shares)	(2,666,221)
Balance as of January 31, 2018 (in shares)	46,359,949	56,840,189
Vested and exercisable as of January 31, 2018 (in shares)	28,990,955
Options Outstanding, Weighted- Average Exercise Price
Balance as of January 31, 2017 (in dollars per share)	$ 7.15
Options granted (in dollars per share)	14.92
Options exercised (in dollars per share)	2.79
Options cancelled/forfeited (in dollars per share)	13.91
Balance as of January 31, 2018 (in dollars per share)	7.75	$ 7.15
Vested and exercisable as of January 31, 2018 (in dollars per share)	$ 5.30
Weighted- Average Remaining Contractual Life (Years)
Weighted Average Remaining Contractual Life (Years)	6 years 3 months 18 days	7 years
Weighted Average Remaining Contractual Life (Years), Vested and exercisable	5 years 8 months 12 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value	$ 574,224	$ 315,502
Aggregate Intrinsic Value, Vested and exercisable	$ 430,325

Equity Incentive Plans - Stock

Equity Incentive Plans - Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Nov. 30, 2016	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost			$ 74,400
Unrecognized compensation cost related to stock awards, weighted-average period			2 years 7 months 6 days
Stock-based compensation expense			$ 150,673	$ 116,668	$ 58,225
Shares underlying outstanding equity awards (in shares)		56,840,189	46,359,949	56,840,189
Class A common stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Closing price of stock (in dollars per share)			$ 20.14
Employee Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Intrinsic value of exercised options			$ 104,900	$ 114,200	$ 29,500
Weighted-average grant date fair value of options granted (in dollars per share)			$ 5.57	$ 5.57	$ 8.38
Total grant date fair value of options vested			$ 42,500	$ 61,800	$ 35,400
Plan modification, number of shares affected (in shares)	800,000
Plan modification, incremental compensation cost		$ 5,900
Performance Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options granted, net of cancellations (in shares)					238,000
Stock-based compensation expense			$ 600	$ 3,300	$ 2,500
Shares underlying outstanding equity awards (in shares)		0	0	0
Plan modification, number of shares affected (in shares)	360,000
Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost related to stock awards, weighted-average period			2 years 7 months 6 days
Plan modification, number of shares affected (in shares)	440,000

Equity Incentive Plans - Summ51

Equity Incentive Plans - Summary of Estimate Fair Values (Details) - $ / shares	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Employee Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days
Expected volatility, minimum			48.00%
Expected volatility, maximum			52.00%
Expected volatility	47.00%	44.00%
Risk-free interest rate, minimum		1.30%	1.50%
Risk-free interest rate, maximum		1.50%	1.90%
Risk-free interest rate	1.90%
Fair value of common stock (in dollars per share)	$ 12.84
Dividend rate	0.00%	0.00%	0.00%
Employee Stock Options | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)			6 years
Fair value of common stock (in dollars per share)		$ 10.37	$ 13.94
Employee Stock Options | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)			7 years 4 months 24 days
Fair value of common stock (in dollars per share)		$ 14.52	$ 19.68
Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, minimum	35.00%
Expected volatility, maximum	39.00%
Expected volatility		41.00%	49.00%
Risk-free interest rate, minimum	0.90%	0.50%	0.10%
Risk-free interest rate, maximum	1.40%	0.90%	0.70%
Dividend rate	0.00%	0.00%	0.00%
Employee Stock Purchase Plan | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 months	6 months	4 months 24 days
Employee Stock Purchase Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	2 years	2 years	1 year 10 months 24 days

Equity Incentive Plans - Restri

Equity Incentive Plans - Restricted Stock Units (Details) - USD ($)	1 Months Ended			12 Months Ended
	Mar. 31, 2018	Aug. 31, 2017	Mar. 30, 2017	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016	Mar. 23, 2018	Mar. 22, 2018	Jan. 31, 2018	Jan. 31, 2017
Weighted-Average Grant Date Fair Value
Aggregate Intrinsic Value									$ 75,500,000
Stock-based compensation expense				$ 150,673,000	$ 116,668,000	$ 58,225,000
Unrecognized compensation cost related to stock awards, weighted-average period				2 years 7 months 6 days
Performance Shares
Weighted-Average Grant Date Fair Value
Stock-based compensation expense				$ 600,000	$ 3,300,000	$ 2,500,000
Restricted stock units
Number of Restricted Stock Units Outstanding
Unvested, beginning balance (in shares)				8,783,024
Granted (in shares)				15,779,364
Vested (in shares)				(5,277,679)
Forfeited (in shares)				(1,602,063)
Unvested, ending balance (in shares)				17,682,646	8,783,024
Weighted-Average Grant Date Fair Value
Unvested, beginning balance (in dollars per share)				$ 13.06
Granted (in dollars per share)				12.16
Vested (in dollars per share)				12.30
Forfeited (in dollars per share)				11.88
Unvested, ending balance (in dollars per share)				$ 12.60	$ 13.06
Aggregate Intrinsic Value									356,117,000	$ 99,863,000
Unrecognized employee compensation cost									$ 187,200,000
Unrecognized compensation cost related to stock awards, weighted-average period				2 years 7 months 6 days
Awards outstanding (in shares)				8,783,024	8,783,024				17,682,646	8,783,024
Granted March 2017 | Performance Shares
Number of Restricted Stock Units Outstanding
Granted (in shares)			750,000
Forfeited (in shares)			(77,000)
Weighted-Average Grant Date Fair Value
Stock-based compensation expense				$ 4,200,000
Unrecognized employee compensation cost									$ 3,300,000
Unrecognized compensation cost related to stock awards, weighted-average period				2 years 2 months 12 days
Granted August 2017 | Performance Shares
Number of Restricted Stock Units Outstanding
Granted (in shares)		464,744
Weighted-Average Grant Date Fair Value
Stock-based compensation expense				$ 0
Minimum | Granted March 2017 | Performance Shares
Weighted-Average Grant Date Fair Value
Award vesting rights, percentage			0.00%
Minimum | Granted August 2017 | Performance Shares
Weighted-Average Grant Date Fair Value
Award vesting rights, percentage		0.00%
Maximum | Granted March 2017 | Performance Shares
Weighted-Average Grant Date Fair Value
Award vesting rights, percentage			150.00%
Maximum | Granted August 2017 | Performance Shares
Weighted-Average Grant Date Fair Value
Award vesting rights, percentage		150.00%
Subsequent Event | Performance Shares
Weighted-Average Grant Date Fair Value
Awards outstanding (in shares)								1,375,210
Subsequent Event | Restricted stock units
Weighted-Average Grant Date Fair Value
Granted (in dollars per share)	$ 21.13
Awards outstanding (in shares)							1,375,210

Equity Incentive Plans - Summ53

Equity Incentive Plans - Summary of Stock-Based Compensation Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 150,673	$ 116,668	$ 58,225
Cost of revenue—product
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	1,630	601	276
Cost of revenue—support
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	9,050	5,639	2,388
Research and development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	71,229	63,495	31,135
Sales and marketing
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	47,687	34,317	16,966
General and administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 21,077	$ 12,616	$ 7,460

Net Loss per Share Attributab54

Net Loss per Share Attributable to Common Stockholders - Summary of Computation of Basic and Diluted Net Loss per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Earnings Per Share [Abstract]
Net loss	$ (177,602)	$ (245,066)	$ (213,752)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	211,609	194,714	82,460
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.84)	$ (1.26)	$ (2.59)

Net Loss per Share Attributab55

Net Loss per Share Attributable to Common Stockholders - Summary of Weighted-average Outstanding Shares Excluded from Computation of Diluted Net Loss per Share Attributable to Common Stockholders (Details) - shares shares in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share, amount	69,710	72,616	65,583
Stock options to purchase common stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share, amount	52,424	63,984	61,795
Restricted stock units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share, amount	15,496	5,216	0
Employee stock purchase plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share, amount	1,544	1,310	170
Early exercised stock options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share, amount	246	2,106	3,618

Income Taxes - Schedule of Geog

Income Taxes - Schedule of Geographical Breakdown of Income (Loss) before Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Income Tax Disclosure [Abstract]
Domestic	$ (135,115)	$ (200,355)	$ (195,019)
International	(38,598)	(42,824)	(17,164)
Loss before provision for income taxes	$ (173,713)	$ (243,179)	$ (212,183)

Income Taxes - Components of Pr

Income Taxes - Components of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Current:
State	$ 525	$ 389	$ 210
Foreign	3,580	1,806	2,198
Total	4,105	2,195	2,408
Deferred:
Foreign	(216)	(308)	(839)
Provision for income taxes	$ 3,889	$ 1,887	$ 1,569

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of the Federal Statutory Income Tax Rate and Effective Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Income Tax Disclosure [Abstract]
Tax at federal statutory rate	$ (57,144)	$ (82,682)	$ (72,142)
State tax, net of federal benefit	351	276	152
Stock-based compensation expense	(9,953)	(5,242)	10,866
Research and development tax credits	(7,629)	(1,570)	(3,832)
Foreign rate differential	18,667	15,878	7,106
Change in valuation allowance	(48,703)	73,863	58,979
Remeasurement of deferred tax assets and liabilities	107,029	0	0
Other	1,271	1,364	440
Provision for income taxes	$ 3,889	$ 1,887	$ 1,569

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Jan. 31, 2018	Jan. 31, 2017
Deferred tax assets:
Net operating loss carryforwards	$ 127,621	$ 173,942
Tax credit carryover	33,105	15,319
Accruals and reserves	1,809	3,112
Deferred revenue	46,570	53,424
Stock-based compensation expense	24,133	26,401
Depreciation and amortization	15,367	7,302
Charitable contribution carryforwards	2,892	4,345
Other	465	0
Total deferred tax assets	251,962	283,845
Valuation allowance	(240,519)	(271,779)
Total deferred tax assets, net of valuation allowance	11,443	12,066
Deferred tax liabilities:
Deferred commissions	(10,383)	(11,222)
Total deferred tax liabilities	(10,383)	(11,222)
Net deferred tax assets, net of valuation allowance	$ 1,060	$ 844

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	Jan. 01, 2018	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Operating Loss Carryforwards [Line Items]
Tax Cuts and Jobs Act of 2017, decrease in deferred tax assets	$ 98,000,000
Deferred tax assets, increase (decrease) in valuation allowance		$ (31,300,000)	$ 90,900,000	$ 68,000,000
Gross unrecognized tax benefit		12,401,000	$ 6,375,000	$ 15,470,000	$ 13,874,000
Current or cumulative interest and penalties related to uncertain tax positions		$ 0
Federal
Operating Loss Carryforwards [Line Items]
Blended tax rate		32.90%
Net operating loss carryforwards		$ 508,900,000
Research and development tax credit carryforwards		26,600,000
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards		331,900,000
Research and development tax credit carryforwards		22,200,000
Non-U.S.
Operating Loss Carryforwards [Line Items]
Undistributed earnings of foreign subsidiaries		$ 20,800,000

Income Taxes - Activity Related

Income Taxes - Activity Related to Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Reconciliation of Unrecognized Tax Benefits
Gross unrecognized tax benefits—beginning balance	$ 6,375	$ 15,470	$ 13,874
Decreases related to tax positions taken during prior years	(24)	(11,286)	(3,969)
Increases related to tax positions taken during prior years	619	0	35
Increases related to tax positions taken during current year	5,431	2,191	5,530
Gross unrecognized tax benefits—ending balance	$ 12,401	$ 6,375	$ 15,470

Segment Information - Additiona

Segment Information - Additional Information (Details)	12 Months Ended
	Jan. 31, 2018segment
Segment Reporting [Abstract]
Number of business activities	1
Number of reportable segments	1

Segment Information - Schedule

Segment Information - Schedule of Revenue by Geographic Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenue	$ 1,023,019	$ 727,977	$ 440,333
United States
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenue	762,391	561,352	343,625
Rest of the world
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenue	$ 260,628	$ 166,625	$ 96,708

Segment Information - Schedul64

Segment Information - Schedule of Long-Lived Assets by Geographic Area (Details) - USD ($) $ in Thousands	Jan. 31, 2018	Jan. 31, 2017
Revenues From External Customers And Long Lived Assets [Line Items]
Property and equipment, net	$ 89,142	$ 81,695
United States
Revenues From External Customers And Long Lived Assets [Line Items]
Property and equipment, net	85,430	78,692
Rest of the world
Revenues From External Customers And Long Lived Assets [Line Items]
Property and equipment, net	$ 3,712	$ 3,003

401(k) Plan - Additional Inform

401(k) Plan - Additional Information (Details)	12 Months Ended
	Jan. 31, 2018
Compensation Related Costs [Abstract]
Maximum annual contributions per employee	100.00%