The RealReal, Inc. (REAL) 10-Q 5 Nov 19 2019 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Oct. 31, 2019
Cover [Abstract]
Entity registrant name	TheRealReal, Inc.
Trading symbol	REAL
Entity central index key	0001573221
Current fiscal year end date	--12-31
Entity filer category	Non-accelerated Filer
Document type	10-Q
Document period end date	Sep. 30, 2019
Document fiscal year focus	2019
Document fiscal period focus	Q3
Amendment flag	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Small Business	false
Entity Interactive Data Current	Yes
Entity common stock, shares outstanding		85,791,236
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-38953
Entity Tax Identification Number	45-1234222
Entity Address, Address Line One	55 Francisco Street
Entity Address, Address Line Two	Suite 600
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94133
City Area Code	855
Local Phone Number	435-5893
Title of 12(b) Security	Common stock, $0.00001 par value
Security Exchange Name	NASDAQ
Document Quarterly Report	true
Document Transition Report	false
Entity Incorporation, State or Country Code	DE

Condensed Balance Sheets (Unaud

Condensed Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 364,995	$ 34,393
Short-term investments	5,290	27,131
Accounts receivable	8,935	7,571
Inventory, net	13,846	10,355
Prepaid expenses and other current assets	13,071	9,696
Total current assets	406,137	89,146
Property and equipment, net	45,715	33,286
Restricted cash		11,234
Other assets	1,518	1,751
Total assets	453,370	135,417
Current liabilities
Accounts payable	5,666	5,149
Accrued consignor payable	39,870	35,259
Other accrued and current liabilities	42,548	41,956
Long-term debt, current portion		5,990
Total current liabilities	88,084	88,354
Long-term debt, net of current portion		3,249
Other noncurrent liabilities	8,050	7,304
Total liabilities	96,134	98,907
Commitments and contingencies (Note 10)
Temporary equity		294,200
Stockholders’ equity (deficit):
Common stock, $0.00001 par value; 500,000,000 and 145,467,774 shares authorized as of September 30, 2019 and December 31, 2018, respectively; 85,759,021 and 8,593,077 shares issued and outstanding as of September 30, 2019 and December 31, 2018, respectively	1
Additional paid-in capital	690,365
Accumulated comprehensive income (loss)	1	(25)
Accumulated deficit	(333,131)	(257,665)
Total stockholders’ equity (deficit)	357,236	(257,690)
Total liabilities, redeemable convertible preferred stock, convertible preferred stock and stockholders’ equity (deficit)	$ 453,370	135,417
Redeemable Convertible Preferred Stock
Current liabilities
Temporary equity		151,381
Convertible Preferred Stock
Current liabilities
Temporary equity		$ 142,819

Condensed Balance Sheets (Una_2

Condensed Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
Temporary equity, shares authorized		105,003,754
Temporary equity, shares issued		104,778,246
Temporary equity, shares outstanding		104,778,246
Common stock, par value	$ 0.00001	$ 0.00001
Common stock, shares authorized	500,000,000	145,467,774
Common stock, shares issued	85,759,021	8,593,077
Common stock, shares, outstanding	85,759,021	8,593,077
Redeemable Convertible Preferred Stock
Temporary equity, par value	$ 0.00001	$ 0.00001
Temporary equity, shares authorized	0	31,053,601
Temporary equity, shares issued	0	31,053,601
Temporary equity, shares outstanding	0	31,053,601
Convertible Preferred Stock
Temporary equity, par value	$ 0.00001	$ 0.00001
Temporary equity, shares authorized	0	73,950,153
Temporary equity, shares issued	0	73,724,645
Temporary equity, shares outstanding	0	73,724,645

Condensed Statements of Operati

Condensed Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue:
Total revenue	$ 80,485	$ 51,839	$ 220,716	$ 145,283
Cost of revenue:
Total cost of revenue	28,257	18,509	80,057	50,569
Gross profit	52,228	33,330	140,659	94,714
Operating expenses:
Marketing	13,390	10,624	36,838	29,534
Operations and technology	37,407	28,257	103,271	72,586
Selling, general and administrative	28,436	16,325	76,110	44,226
Total operating expenses	79,233	55,206	216,219	146,346
Loss from operations	(27,005)	(21,876)	(75,560)	(51,632)
Interest income	1,902	437	2,918	602
Interest expense	(60)	(204)	(572)	(927)
Other expense, net	(119)	(205)	(2,106)	(1,592)
Loss before provision for income taxes	(25,282)	(21,848)	(75,320)	(53,549)
Provision (benefit) for income taxes	(8)	37	51	37
Net loss	(25,274)	(21,885)	(75,371)	(53,586)
Accretion of redeemable convertible preferred stock to redemption value		(3,200)	(3,355)	(5,651)
Net loss attributable to common stockholders	$ (25,274)	$ (25,085)	$ (78,726)	$ (59,237)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.30)	$ (3)	$ (2.28)	$ (7.12)
Shares used to compute net loss per share attributable to common stockholders, basic and diluted	84,634,956	8,349,403	34,556,485	8,321,296
Consignment and Service Revenue
Revenue:
Total revenue	$ 69,790	$ 45,744	$ 186,740	$ 128,921
Cost of revenue:
Total cost of revenue	19,446	13,157	52,593	37,083
Direct Revenue
Revenue:
Total revenue	10,695	6,095	33,976	16,362
Cost of revenue:
Total cost of revenue	$ 8,811	$ 5,352	$ 27,464	$ 13,486

Condensed Statements of Compreh

Condensed Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (25,274)	$ (21,885)	$ (75,371)	$ (53,586)
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on investments	(4)	(8)	26	(2)
Comprehensive loss	$ (25,278)	$ (21,893)	$ (75,345)	$ (53,588)

Condensed Statements of Redeema

Condensed Statements of Redeemable Convertible Preferred Stock, Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	Redeemable Convertible Preferred Stock	Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Gain (Loss)	Accumulated Deficit
Beginning balance, shares at Dec. 31, 2017		12,956,724	69,834,789
Beginning balance at Dec. 31, 2017		$ 50,367	$ 122,990
Beginning balance, shares at Dec. 31, 2017				8,287,983
Beginning balance at Dec. 31, 2017	$ (176,986)				$ 4,591	$ (6)	$ (181,571)
Accretion of redeemable convertible preferred stock to redemption value	(1,109)				(1,109)
Accretion of redeemable convertible preferred stock to redemption value		$ 1,109
Issuance of common stock upon exercise of options	39				39
Issuance of common stock upon exercise of options, shares				18,621
Stock-based compensation expense	545				545
Other comprehensive income	6					6
Net loss	(14,106)						(14,106)
Ending balance, shares at Mar. 31, 2018		12,956,724	69,834,789
Ending balance at Mar. 31, 2018		$ 51,476	$ 122,990
Ending balance, shares at Mar. 31, 2018				8,306,604
Ending balance at Mar. 31, 2018	(191,611)				4,066		(195,677)
Beginning balance, shares at Dec. 31, 2017		12,956,724	69,834,789
Beginning balance at Dec. 31, 2017		$ 50,367	$ 122,990
Beginning balance, shares at Dec. 31, 2017				8,287,983
Beginning balance at Dec. 31, 2017	(176,986)				4,591	(6)	(181,571)
Net loss	(53,586)
Ending balance, shares at Sep. 30, 2018		31,053,601	73,724,645
Ending balance at Sep. 30, 2018		$ 148,110	$ 142,819
Ending balance, shares at Sep. 30, 2018				8,448,188
Ending balance at Sep. 30, 2018	(233,525)				1,640	(8)	(235,157)
Beginning balance, shares at Mar. 31, 2018		12,956,724	69,834,789
Beginning balance at Mar. 31, 2018		$ 51,476	$ 122,990
Beginning balance, shares at Mar. 31, 2018				8,306,604
Beginning balance at Mar. 31, 2018	(191,611)				4,066		(195,677)
Issuance of convertible preferred stock upon conversion of notes, net of issuance costs		$ 5,452	$ 10,202
Issuance of convertible preferred stock upon conversion of notes, net of issuance costs, shares		1,067,550	1,997,709
Loss on extinguishment of convertible notes	(370)				(370)
Issuance of convertible preferred stock, net of issuance costs		$ 86,640
Issuance of convertible preferred stock, net of issuance costs, shares		17,029,327
Accretion of redeemable convertible preferred stock to redemption value	(1,342)				(1,342)
Accretion of redeemable convertible preferred stock to redemption value		$ 1,342
Issuance of common stock upon exercise of options	24				24
Issuance of common stock upon exercise of options, shares				17,502
Stock-based compensation expense	681				681
Net loss	(17,595)						(17,595)
Ending balance, shares at Jun. 30, 2018		31,053,601	71,832,498
Ending balance at Jun. 30, 2018		$ 144,910	$ 133,192
Ending balance, shares at Jun. 30, 2018				8,324,106
Ending balance at Jun. 30, 2018	(210,213)				3,059		(213,272)
Issuance of convertible preferred stock upon conversion of notes, net of issuance costs			$ 9,627
Issuance of convertible preferred stock upon conversion of notes, net of issuance costs, shares			1,892,147
Accretion of redeemable convertible preferred stock to redemption value	(3,200)				(3,200)
Accretion of redeemable convertible preferred stock to redemption value		$ 3,200
Compensation expense related to stock sales by current and former employees	847				847
Issuance of common stock upon exercise of options	194				194
Issuance of common stock upon exercise of options, shares				124,083
Stock-based compensation expense	740				740
Other comprehensive income	(8)					(8)
Net loss	(21,885)						(21,885)
Ending balance, shares at Sep. 30, 2018		31,053,601	73,724,645
Ending balance at Sep. 30, 2018		$ 148,110	$ 142,819
Ending balance, shares at Sep. 30, 2018				8,448,188
Ending balance at Sep. 30, 2018	$ (233,525)				1,640	(8)	(235,157)
Beginning balance, shares at Dec. 31, 2018	104,778,246	31,053,601	73,724,645
Beginning balance at Dec. 31, 2018	$ 294,200	$ 151,381	$ 142,819
Beginning balance, shares at Dec. 31, 2018				8,593,077
Beginning balance at Dec. 31, 2018	(257,690)					(25)	(257,665)
Issuance of convertible preferred stock, net of issuance costs		$ 43,572	$ 26,279
Issuance of convertible preferred stock, net of issuance costs, shares		6,350,345	3,831,766
Accretion of redeemable convertible preferred stock to redemption value	(3,355)				(3,260)		(95)
Accretion of redeemable convertible preferred stock to redemption value		$ 3,355
Compensation expense related to stock sales by current and former employees	819				819
Issuance of common stock upon exercise of options	1,319				1,319
Issuance of common stock upon exercise of options, shares				739,053
Issuance of common stock upon exercise of warrants, shares				4,935
Issuance of common stock upon exercise of warrants	13				13
Stock-based compensation expense	1,109				1,109
Other comprehensive income	28					28
Net loss	(23,222)						(23,222)
Ending balance, shares at Mar. 31, 2019		37,403,946	77,556,411
Ending balance at Mar. 31, 2019		$ 198,308	$ 169,098
Ending balance, shares at Mar. 31, 2019				9,337,065
Ending balance at Mar. 31, 2019	$ (280,979)					3	(280,982)
Beginning balance, shares at Dec. 31, 2018	104,778,246	31,053,601	73,724,645
Beginning balance at Dec. 31, 2018	$ 294,200	$ 151,381	$ 142,819
Beginning balance, shares at Dec. 31, 2018				8,593,077
Beginning balance at Dec. 31, 2018	(257,690)					(25)	(257,665)
Net loss	(75,371)
Ending balance, shares at Sep. 30, 2019		0	0
Ending balance, shares at Sep. 30, 2019				85,759,021
Ending balance at Sep. 30, 2019	357,236			$ 1	690,365	1	(333,131)
Beginning balance, shares at Mar. 31, 2019		37,403,946	77,556,411
Beginning balance at Mar. 31, 2019		$ 198,308	$ 169,098
Beginning balance, shares at Mar. 31, 2019				9,337,065
Beginning balance at Mar. 31, 2019	(280,979)					3	(280,982)
Stock issuance costs		$ (80)	$ 4
Issuance of common stock upon exercise of options	423			$ 1	422
Issuance of common stock upon exercise of options, shares				358,459
Issuance of common stock upon exercise of warrants, shares				5,742
Issuance of common stock upon exercise of warrants	20				20
Stock-based compensation expense	1,287				1,287
Other comprehensive income	2					2
Net loss	(26,875)						(26,875)
Ending balance, shares at Jun. 30, 2019		37,403,946	77,556,411
Ending balance at Jun. 30, 2019		$ 198,228	$ 169,102
Ending balance, shares at Jun. 30, 2019				9,701,266
Ending balance at Jun. 30, 2019	(306,122)			$ 1	1,729	5	(307,857)
Conversion of redeemable convertible preferred stock to common stock in connection with initial public offering	198,228				198,228
Conversion of redeemable convertible preferred stock to common stock in connection with initial public offering, shares		(37,403,946)
Conversion of redeemable convertible preferred stock to common stock in connection with initial public offering		$ (198,228)
Conversion of redeemable convertible preferred stock to common stock in connection with initial public offering, shares				19,585,426
Conversion of convertible preferred stock to common stock in connection with initial public offering	169,102				169,102
Conversion of convertible preferred stock to common stock in connection with initial public offering, shares			(77,556,411)
Conversion of convertible preferred stock to common stock in connection with initial public offering			$ (169,102)
Conversion of convertible preferred stock to common stock in connection with initial public offering, shares				38,778,180
Conversion of convertible preferred stock warrants to common stock warrants in connection with initial public offering	2,710				2,710
Issuance of common stock in connection with initial public offering, net of issuance costs of $5,428	315,422				315,422
Issuance of common stock in connection with initial public offering, net of issuance costs of $5,428, shares				17,250,000
Issuance of common stock upon vesting of restricted stock units, net of shares withheld for employee taxes	(20)				(20)
Issuance of common stock upon vesting of restricted stock units, net of shares withheld for employee taxes, shares				1,969
Issuance of common stock upon exercise of options	674				674
Issuance of common stock upon exercise of options, shares				352,638
Issuance of common stock upon exercise of warrants, shares				89,542
Stock-based compensation expense	2,520				2,520
Other comprehensive income	(4)					(4)
Net loss	(25,274)						(25,274)
Ending balance, shares at Sep. 30, 2019		0	0
Ending balance, shares at Sep. 30, 2019				85,759,021
Ending balance at Sep. 30, 2019	$ 357,236			$ 1	$ 690,365	$ 1	$ (333,131)

Condensed Statements of Redee_2

Condensed Statements of Redeemable Convertible Preferred Stock, Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018
Initial Public Offering
Issuance of stock, net of issuance costs	$ 5,428
Series G Redeemable Convertible Preferred Stock
Convertible preferred stock upon conversion of notes, net of issuance costs					$ 190
Stock issuance costs					3,360
Series G Convertible Preferred Stock
Convertible preferred stock upon conversion of notes, net of issuance costs				$ 373	$ 355
Series H Redeemable Convertible Preferred Stock
Stock issuance costs		$ 166	$ 86
Series H Convertible Preferred Stock
Stock issuance costs		$ 59	$ 63

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net loss	$ (75,371)	$ (53,586)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation and amortization	9,537	6,489
Stock-based compensation expense	4,916	1,966
Change in fair value of convertible note derivative liability		1,248
Bad debt expense	1,208	609
Compensation expense related to stock sales by current and former employees	819	847
Change in fair value of convertible preferred stock warrant liability	2,100	388
Accrued interest on convertible notes		223
Accretion of unconditional endowment grant liability	70	85
Accretion of debt discounts	11	104
Amortization of premiums on short-term investments	38	27
Changes in operating assets and liabilities:
Accounts receivable	(2,572)	(2,854)
Inventory, net	(3,491)	(1,607)
Prepaid expenses and other current assets	(3,375)	(10,060)
Other assets	136	445
Accounts payable	1,394	2,752
Accrued consignor payable	4,611	1,537
Other accrued and current liabilities	494	10,000
Other noncurrent liabilities	1,356	1,762
Net cash used in operating activities	(58,119)	(39,625)
Cash flow from investing activities:
Purchases of short-term investments	(12,169)	(24,237)
Proceeds from maturities of short-term investments	33,998	7,600
Proceeds from sale of short-term investments		7,023
Capitalized proprietary software development costs	(6,670)	(4,204)
Purchases of property and equipment	(16,111)	(8,781)
Net cash used in investing activities	(952)	(22,599)
Cash flow from financing activities:
Proceeds from issuance of common stock in initial public offering, net of issuance costs	315,486
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs	43,492	86,640
Proceeds from issuance of convertible preferred stock, net of issuance costs	26,283	9,627
Proceeds from issuance of convertible notes, net of issuance costs		14,273
Proceeds from exercise of stock options and common stock warrants	2,448	257
Taxes paid related to net share settlement of equity awards	(20)
Issuance cost paid related to conversion of convertible notes		(545)
Repayment of debt	(9,250)	(2,750)
Net cash provided by financing activities	378,439	107,502
Net increase in cash, cash equivalents and restricted cash	319,368	45,278
Cash, cash equivalents, and restricted cash
Beginning of period	45,627	20,660
End of period	364,995	65,938
Supplemental disclosures of cash flow information
Cash paid for interest	532	488
Cash paid for income taxes		35
Supplemental disclosures of non-cash investing and financing activities
Issuance of convertible preferred stock upon extinguishment of convertible notes		10,557
Issuance of redeemable convertible preferred stock upon extinguishment of convertible notes		5,642
Accretion of redeemable convertible preferred stock to redemption value	3,355	5,651
Loss on extinguishment of convertible notes		370
Purchases of property and equipment included in accounts payable	(877)	$ (767)
Deferred offering costs in accounts payable and accrued liabilities	28
Conversion of convertible preferred stock warrants in connection with IPO	2,710
Redeemable Convertible Preferred Stock
Supplemental disclosures of non-cash investing and financing activities
Conversion of convertible stock in connection with IPO	198,228
Convertible Preferred Stock
Supplemental disclosures of non-cash investing and financing activities
Conversion of convertible stock in connection with IPO	$ 169,102

Description of Business and Bas

Description of Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of Business and Basis of Presentation	Note 1. Description of Business and Basis of Presentation Organization and Description of Business The RealReal, Inc. (the “Company”) is an online marketplace for authenticated, consigned luxury goods across multiple categories, including women’s, men’s, kids’, jewelry and watches, and home and art. The Company was incorporated in the state of Delaware on March 29, 2011 and is headquartered in San Francisco, California. Basis of Presentation The accompanying unaudited condensed financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and the requirements of the U.S. Securities and Exchange Commission (the “SEC”) for interim reporting. The Company’s functional and reporting currency is the U.S. dollar. The condensed balance sheet as of December 31, 2018 included herein was derived from the audited financial statements as of that date. The accompanying unaudited condensed financial statements have been prepared on the same basis as the annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to state fairly the Company’s financial position, results of operations, comprehensive loss, redeemable convertible preferred stock, convertible preferred stock, and stockholders’ equity (deficit), and cash flows for the periods presented. These unaudited condensed financial statements should be read in conjunction with the Company’s financial statements and notes included in the final prospectus filed with the SEC pursuant to Rule 424(b) under the Securities Act of 1933, as amended on June 28, 2019 (the “Prospectus”). Initial Public Offering The Company’s registration statement on Form S-1 (the “IPO Registration Statement”) related to its initial public offering (“IPO”) was declared effective on June 27, 2019, and the Company’s common stock began trading on the Nasdaq Global Select Market on June 28, 2019. On July 2, 2019, the Company completed its IPO, selling 15,000,000 shares of common stock at a price to the public of $20.00 per share, plus an additional 2,250,000 shares of common stock at a price to the public of $20.00 per share pursuant to the exercise of the underwriters’ option to purchase additional shares. The Company received aggregate net proceeds of $315.5 million after deducting underwriting discounts and commissions of $24.1 million and issuance costs of $5.4 million. Immediately p rior to the completion of the IPO, the Company filed its Amended and Restated Certificate of Incorporation, which authorizes a total of 500,000,000 shares of common stock, and 50,000,000 shares of undesignated preferred stock The Company recorded the conversion of 114,960,357 shares of convertible preferred stock and redeemable convertible preferred stock then outstanding into 58,363,606 shares of common stock to additional paid-in capital. All outstanding preferred stock warrants converted into an aggregate of 103,563 common stock warrants Reverse Stock Split On June 13, 2019 the Company effected a reverse split of shares of the Company’s common stock on a 1-for-2 basis (the “Reverse Stock Split”). All issued and outstanding shares of common stock, warrants for common stock, options to purchase common stock and the related per share amounts contained in the financial statements have been retroactively adjusted to reflect this Reverse Stock Split for all periods presented. The par value and authorized shares of common stock were not adjusted as a result of the Reverse Stock Split. Additionally, the authorized, issued and outstanding shares of redeemable convertible preferred stock and convertible preferred stock and their related per share amounts, other than the conversion price per share, were not adjusted as a result of the Reverse Stock Split.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Note Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of expenses during the reporting period. Significant items subject to such estimates and assumptions include those related to revenue recognition, including the returns reserve and material right related to the Company’s tiered consignor commission plan, valuation of inventory, stock-based compensation, redemption value of redeemable convertible preferred stock, and other contingencies. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could differ from those estimates. Net Loss per Share Attributable to Common Stockholders The Company follows the two-class method when computing net loss per common share when shares are issued that meet the definition of participating securities. The two-class method determines net loss per common share for each class of common stock and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to common stockholders for the period to be allocated between common stock and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed. The Company’s redeemable convertible preferred stock and convertible preferred stock contractually entitles the holders of such shares to participate in dividends but does not contractually require the holders of such shares to participate in the Company’s losses. For periods in which the Company reports net losses, diluted net loss per common share attributable to common stockholders is the same as basic net loss per common share attributable to common stockholders, because potentially dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. Revenue Recognition The Company generates revenue from the sale of pre-owned luxury goods through its online marketplace. Consignment and Service Revenue The Company provides a service to sell pre-owned luxury goods on behalf of consignors to buyers through its online marketplace and retail locations. The Company retains a percentage of the proceeds received as payment for its consignment service, which the Company refers to as its take rate. The Company reports consignment revenue on a net basis as an agent and not the gross amount collected from the buyer. Title to the consigned goods remain with the consignor until transferred to the end customer subsequent to purchase of the consigned goods. The Company does not take title of consigned goods at any time except in certain cases where returned goods become Company-owned inventory. The Company recognizes consignment revenue upon purchase of the consigned good by the buyer as its performance obligation of providing consignment services to the consignor is satisfied at that point. Consignment revenue is recognized net of certain buyer incentives and estimated returns and cancellations. The Company recognizes a returns reserve, based on historical experience, which is recorded in other accrued and current liabilities on the balance sheets (see Note 5). Sales tax assessed by governmental authorities is excluded from revenue. Certain transactions provide consignors with a material right resulting from the tiered consignor commission plan. Under this plan, the amount an individual consignor receives for future sales of consigned goods may be dependent on previous consignment sales for that consignor within his/her consignment period. Accordingly, in certain consignment transactions, a small portion of the Company’s consignment revenue is allocated to such material right using the portfolio method and recorded as deferred revenue. The Company charges shipping fees to buyers and has elected to treat shipping and handling activities performed after control transfers to the buyer as fulfillment activities. All outbound shipping and handling costs are accounted for as fulfillment costs in cost of consignment and service revenue at the time revenue is recognized. The Company also generates subscription revenue from monthly memberships allowing buyers early access to shop for luxury goods. The buyers receive the early access and other benefits over the term of the subscription period, which represents a single stand-ready performance obligation. Therefore, the subscription fees paid by the buyer are recognized over the monthly subscription period. Subscription revenue was not material in the three or nine months ended September 30, 2019 and 2018. Direct Revenue The Company generates direct revenue from the sale of Company-owned inventory. The Company recognizes direct revenue upon shipment of the purchased good to the buyer as its performance obligation, consisting of the sale of goods, is satisfied at this point. Direct revenue is recognized net of incentives and estimated returns. Sales tax assessed by governmental authorities is excluded from revenue. Incentives Promotional incentives, which include basket promotional code discounts and other credits, may periodically be offered to consignors and buyers. These are treated as a reduction of consignment and service revenue and direct revenue. Additionally, the Company may offer site credits to buyers on current transactions to be applied towards future transactions, which are accounted as site credit liabilities and included in other accrued and current liabilities on the balance sheets. Contract Liabilities The Company’s contractual liabilities consist of deferred revenue for material rights primarily related to the tiered consignor commission plan totaling $3.4 million as of September 30, 2019 and Cost of Revenue Cost of revenue for consignment and services and direct revenue consist of shipping costs, credit card fees, packaging, customer service and website hosting services. Cost of direct revenue also includes the cost of goods sold. Stock-based Compensation Stock-based compensation expense related to employees is measured based on the grant-date fair value of the awards. Compensation expense is recognized in the statements of operations over the period during which the employee is required to perform services in exchange for the award (the vesting period of the applicable award) using the straight-line method. The Company estimates the fair value of stock options granted using the Black-Scholes option pricing model and accounts for forfeitures as they occur. The fair value of restricted stock units (“RSUs”) is estimated based on the fair market value of the Company’s common stock on the date of grant, which is determined based on the closing price of the Company’s common stock. Historically, certain employees were able to sell their shares of the Company’s common stock to the Company’s existing investors. In such secondary sale transactions, the Company recorded the difference in purchase price and the fair value of such shares as compensation expense within selling, general and administrative in the statement of operations and a corresponding credit to additional paid-in capital. Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments purchased with original maturities of three months or less from the purchase date to be cash equivalents. Cash equivalents consist primarily of amounts invested in reverse repurchase agreement (“RRAs”). RRAs are collateralized by deposits in the form of United States government securities and obligations for an amount not less than 102% of their value. The Company has a policy that the collateral has at least an A (or equivalent) credit rating. The Company utilizes a third-party custodian to manage the exchange of funds and ensure that collateral received is maintained at 102% of the value of the RRAs on a daily basis. RRAs with stated maturities of greater than three months from the date of purchase are classified as short-term investments. Restricted cash consists of cash deposited with a financial institution as collateral for the Company’s letters of credit for its facility leases and the Company’s credit cards. As of September 30, 2019 and December 31, 2018, the Company had letters of credit outstanding and collateral accounts in the amounts of zero and $11.2 million, respectively. The following table provides a reconciliation of cash, cash equivalents and restricted cash that sum to the total of the same amounts shown in the statements of cash flows (in thousands): September 30, 2019 September 30, 2018 Cash and cash equivalents $ 364,995 $ 54,704 Restricted cash — 11,234 Total cash, cash equivalents and restricted cash $ 364,995 $ 65,938 Inventory, Net Inventory primarily consists of finished goods arising from goods returned after the consignor has been paid, upon which the Company assumes the title to the goods until it is resold and recognizes it as inventory in an amount equal to that paid to the consignor. The Company also periodically purchases finished goods directly from vendors. Inventory is valued at the lower of cost and net realizable value using the specific identification method and the Company records provisions, as appropriate, to write down obsolete and excess inventory to estimated net realizable value. After the inventory value is reduced, adjustments are not made to increase it from the estimated net realizable value. The inventory reserve, which reduces inventory on the balance sheets, was $1.4 million and $0.7 million as of September 30, 2019 and December 31, 2018, respectively. Software Development Costs Proprietary software includes the costs of developing the Company’s internal proprietary business platform. The Company capitalizes qualifying proprietary software development costs that are incurred during the application development stage. Capitalization of costs begins when two criteria are met: (1) the preliminary project stage is completed and (2) it is probable that the software will be completed and used for its intended function. Such costs are capitalized in the period incurred. Capitalization ceases and amortization begins when the software is substantially complete and ready for its intended use, including the completion of all significant testing. Costs related to preliminary project activities and post-implementation operating activities are expensed as incurred. Accretion of Redeemable Convertible Preferred Stock The carrying value of the redeemable convertible preferred stock that is probable of redemption is accreted to redemption value from the date of issuance to the earliest redemption date using the effective interest method. Increases to the carrying value of redeemable convertible preferred stock recognized in each period are charged to additional paid-in capital, or in the absence of additional paid-in capital, charged to accumulated deficit. Convertible Preferred Stock Warrant Liability The Company issued convertible preferred stock warrants in conjunction with the issuance of debt. Such warrants were recorded as other noncurrent liabilities on the balance sheets at their estimated fair value because the shares underlying the warrants may obligate the Company to transfer assets to the holders at a future date under certain circumstances such as a deemed liquidation event. The warrants are subject to re-measurement at each balance sheet date and the change in fair value, if any, is included in other expense, net. The Company continued to remeasure these warrants until the earlier of the expiration, exercise or conversion of the convertible preferred stock warrants into common warrants, which occurred upon the completion of the IPO on July 2, 2019. In connection with the completion of the IPO, the convertible preferred stock warrants automatically converted into common stock warrants. Upon conversion of the convertible preferred stock warrants, the related convertible preferred stock warrant liability was reclassified to additional paid-in capital. Leases Leases are reviewed for classification as operating or capital leases. For operating leases, the Company recognizes rent on a straight-line basis over the term of the lease. The Company records the difference between cash payments and rent expense recognized as a deferred rent liability included in other accrued and current liabilities and other noncurrent liabilities on the balance sheets. Incentives granted under the Company’s facility leases, including allowances to fund leasehold improvements, are deferred and are recognized as adjustments to rental expense on a straight-line basis over the term of the lease. Concentrations of Credit Risks Financial instruments that potentially subject the Company to concentrations of credit risk consist of cash and cash equivalents. At times, such amount may exceed federally-insured limits. The Company reduces credit risk by placing its cash and cash equivalents with major credit-worthy financial institutions within the United States. As of September 30, 2019 and December 31, 2018, there were no customers that represented 10% or more of the Company’s accounts receivable balance and there were no customers that individually exceeded 10% of the Company’s total revenue for each of the three and nine months ended September 30, 2019 and 2018. Recently Adopted Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers In June 2018, the FASB issued ASU 2018-08, Clarifying the Scope and the Accounting Guidance for Contributions Received and Contributions Made (Topic 958) In August 2018, the FASB issued ASU 2018-15 , Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40) Recently Issued Accounting Pronouncements In January 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities (Subtopic 825-10) fiscal years beginning after December 15, 2018, and interim periods within fiscal years beginning after December 15, 2019 In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments (Topic 326) The Company does not expect the adoption of this standard to have a material impact on the operating results. In June 2018, the FASB issued ASU 2018-07, Compensation—Stock Compensation (Topic 718), In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820)

Cash, Cash Equivalents and Shor

Cash, Cash Equivalents and Short Term Investments	9 Months Ended
	Sep. 30, 2019
Cash And Cash Equivalents [Abstract]
Cash, Cash Equivalents, and Short-Term Investments	Note 3. Cash, Cash Equivalents and Short-Term Investments The following tables summarize the estimated value of the Company’s cash, cash equivalents and short-term investments (in thousands): September 30, 2019 Amortized Cost Unrealized Gain Unrealized Loss Fair Value Cash and cash equivalents: Cash $ 119,130 $ — $ — $ 119,130 Money market fund 231,865 — — 231,865 Corporate bonds 2,000 — — 2,000 Reverse repurchase agreements 12,000 — — 12,000 Total cash and cash equivalents $ 364,995 $ — $ — $ 364,995 Short-term investments: U.S. corporate bonds $ 2,282 $ 1 — $ 2,283 International corporate bonds 3,007 — — 3,007 Total short-term investments $ 5,289 $ 1 $ — $ 5,290 December 31, 2018 Amortized Cost Unrealized Gain Unrealized Loss Fair Value Cash and cash equivalents: Cash $ 10,253 $ — $ — $ 10,253 Money market fund 140 — — 140 Reverse repurchase agreements 24,000 — — 24,000 Total cash and cash equivalents $ 34,393 $ — $ — $ 34,393 Short-term investments: U.S. corporate bonds $ 21,184 $ — $ (19 ) $ 21,165 International corporate bonds 5,972 — (6 ) 5,966 Total short-term investments $ 27,156 $ — $ (25 ) $ 27,131 As of September 30, 2019 and December 31, 2018, the contractual maturity for the short-term investments is less than one year. For the three and nine months ended September 30, 2019 and 2018, the Company recognized no material realized gains or losses on short-term investments.

Fair Value Measurement

Fair Value Measurement	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurement	Note 4. Fair Value Measurement Assets and liabilities recorded at fair value on a recurring basis on the balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be 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. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level 1—Observable inputs such as unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date. Level 2—Inputs (other than quoted prices included in Level 1) are either directly or indirectly observable for the asset or liability. These include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active. Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. There were no transfers between Level 1, Level 2 or Level 3 of the fair value hierarchy during the periods presented. The following tables provide the financial instruments measured at fair value (in thousands): September 30, 2019 Level 1 Level 2 Level 3 Total Assets Cash equivalents: Money market fund $ 231,865 $ — $ — $ 231,865 Corporate bonds — 2,000 — 2,000 Reverse repurchase agreements — 12,000 — 12,000 Total cash equivalents $ 231,865 $ 14,000 $ — $ 245,865 Short-term investments: U.S. corporate bonds $ — $ 2,283 $ — $ 2,283 International corporate bonds — 3,007 — 3,007 Total short-term investments $ — $ 5,290 $ — $ 5,290 Total assets $ 231,865 $ 19,290 $ — $ 251,155 December 31, 2018 Level 1 Level 2 Level 3 Total Assets Cash equivalents: Money market fund $ 140 $ — $ — $ 140 Reverse repurchase agreements — 24,000 — 24,000 Total cash equivalents $ 140 $ 24,000 $ — $ 24,140 Short-term investments: U.S. corporate bonds $ — $ 21,165 $ — $ 21,165 International corporate bonds — 5,966 — 5,966 Total short-term investments $ — $ 27,131 $ — $ 27,131 Total assets $ 140 $ 51,131 $ — $ 51,271 Liabilities Convertible preferred stock warrant liability $ — $ — $ 610 $ 610 Total liabilities $ — $ — $ 610 $ 610 The fair value of the convertible preferred stock warrant liability on the date of issuance and each re-measurement date was estimated using the Black‑Scholes option pricing model. Inputs used to determine the estimated fair value as of each valuation date included expected term of the warrants, the risk-free interest rate, volatility, and the fair value of underlying shares. Due to the nature of these inputs, the valuation of the warrants is considered a Level 3 measurement. The following table presents a rollforward of the fair value of the level 3 liabilities recorded at fair value at September 30, 2019 (in thousands): Convertible Preferred Stock Warrant Liability Balance as of December 31, 2018 $ 610 Changes in estimated fair value 2,100 Reclass to additional paid-in capital upon conversion to common stock warrants (2,710 ) Balance as of September 30, 2019 $ —

Balance Sheet Components

Balance Sheet Components	9 Months Ended
	Sep. 30, 2019
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	Note 5. Balance Sheet Components Property and Equipment, Net Property and equipment, net is recorded at cost less accumulated depreciation and amortization. Depreciation and amortization are recorded on a straight-line basis over the estimated useful lives of the respective assets. Property and equipment, net consists of the following (in thousands): September 30, 2019 December 31, 2018 Proprietary software $ 20,721 $ 14,052 Furniture and equipment 18,463 12,665 Automobiles 521 346 Leasehold improvements 34,954 25,702 74,659 52,765 Less: accumulated depreciation and amortization (28,944 ) (19,479 ) Property and equipment, net $ 45,715 $ 33,286 Depreciation and amortization expense on property and equipment was $3.5 million and $2.4 million for the three months ended September 30, 2019 and 2018, respectively, and $9.5 million and $6.5 million for the nine months ended September 30, 2019 and 2018, respectively. Other Accrued and Current Liabilities Other accrued and current liabilities consist of the following (in thousands): September 30, 2019 December 31, 2018 Returns reserve $ 12,163 $ 14,311 Accrued compensation 8,134 8,078 Site credit liability 5,612 4,700 Accrued sales tax and other taxes 4,703 4,476 Deferred revenue 3,582 3,184 Accrued marketing and outside services 4,963 4,152 Other 3,391 3,055 Other accrued and current liabilities $ 42,548 $ 41,956

Debt and Convertible Preferred

Debt and Convertible Preferred Stock Warrants	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Debt and Convertible Preferred Stock Warrants	Note 6. Debt and Convertible Preferred Stock Warrants Term Loans In 2013, the Company entered into an agreement to obtain a term loan facility (“Term Loan Facility”) in the amount of $5.0 million for general corporate purposes and working capital expenditures. In 2014, 2015 and 2016, the Company amended its Term Loan Facility to increase the amount borrowed under the facility by $11.6 million. The Term Loan Facility is secured by liens on substantially all of the Company’s present and future assets. The Term Loan Facility includes affirmative, negative and financial covenants that restrict the Company’s ability to, among other things, incur additional indebtedness, make investments, sell or otherwise dispose of assets, pay dividends or repurchase stock. The Term Loan Facility’s financial covenants required the Company to achieve at least 80% of its forecasted gross revenue and a liquidity ratio on a monthly basis. In 2017, the Company executed the eighth amendment (“Eight Amendment”) to the Term Loan Facility. The Eighth Amendment refinanced the $15.0 million repayment schedule to be two term loans, which included a $7.5 million interest only term loan with a maturity date of January 31, 2019 (“Term Loan I”), and the remaining $7.5 million under the existing Term Loan Facility with a maturity date of January 1, 2020 (“Term Loan II”) (together the “Term Loans”). In 2018, the Company entered into the ninth, tenth, eleventh, and twelfth amendment (“Ninth Amendment,” “Tenth Amendment,” “Eleventh Amendment” and “Twelfth Amendment”) to the existing Term Loans. The Ninth Amendment removed the liquidity ratio covenant, amended Term Loan I to be due in 30 equal monthly installments, plus all accrued interest, beginning July 31, 2018, increased the variable annual interest rate from 0.10% above the prime rate to 0.35% above the prime rate and extended the maturity date of Term Loan I to January 31, 2021. The Eighth Amendment and Ninth Amendment required the Company to pay a combined success fee of $0.3 million upon (1) any sale or licensing of all or substantially all of the Company’s assets, (2) any change in control of the Company, or (3) an initial public offering of the Company’s equity securities. The Ninth Amendment also required the Company to pay an additional success fee of $0.1 million upon the sale or issuance of the Company’s equity securities or subordinated debt securities for net cash proceeds of at least $50.0 million on or prior to June 30, 2018. The Company paid the $0.1 million success fee upon the Series G convertible preferred stock financing in June 2018 and the $0.3 million success fee related to its IPO in July 2019. The Tenth and Twelfth Amendments adjusted and waived certain covenant violations which were subsequently amended and met. The Eleventh Amendment provided an additional letter of credit of $1.5 million for corporate credit cards with a maturity date of August 1, 2019. On July 26, 2019 the Company fully repaid the principal of its Terms Loans in the amount of $6.5 million. With the repayment of the term loans, the Company was no longer subject to debt covenants as of September 30, 2019. During the three months ended, September 30, 2019 and 2018, the Company recorded interest expense related to the Term Loans of $0.1 million and $0.2 million, respectively. During the nine months ended September 30, 2019 and 2018, the Company recorded interest expense related to the Term Loans of $0.6 million and $0.5 million, respectively. Warrants Issued with Term Loan Facility During the period from 2013 to 2016, in connection with the Term Loan Facility, the Company issued convertible preferred stock warrants, which included warrants to purchase 131,652 shares of its Series B convertible preferred stock with an exercise price of $1.03 per share, 6,868 shares of its Series C convertible preferred stock with an exercise price of $2.18 per share, 43,010 shares of its Series D convertible preferred stock with an exercise price of $2.79 per share and 25,597 shares of its Series E convertible preferred stock with an exercise price of $2.93 per share (together the “Convertible Preferred Stock Warrants”). The Convertible Preferred Stock Warrants were exercisable from the date of issuance and have a 10-year term. The initial estimated fair value of the Convertible Preferred Stock Warrants was recorded as convertible preferred stock warrant liability with an offset to the debt discount associated with the Term Loan Facility. The debt discount is amortized to interest expense over the repayment period of the loan using the effective-interest method. All convertible Preferred Stock Warrants were converted to common stock warrants and exercised through net share settlement in July 2019. No warrants were outstanding as of September 30, 2019.

Convertible Notes

Convertible Notes	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Convertible Notes	Note 7. Convertible Notes In April 2018, the Company issued $14.4 million in convertible notes (“Convertible Notes”) to existing shareholders of redeemable convertible and convertible preferred stock. Interest accrued on the principal balance at an annual rate of 8%. Principal and accrued interest were due at the earliest of (1) the one-year anniversary of the issuance date, (2) event of default and (3) a change of control, defined as either a merger, sale of stock or assets or other form of transaction. The maturity date could be extended if agreed upon by the Company and investors holding the convertible notes representing at least 80% of the outstanding amount at such time. On change of control, the holders of convertible notes could elect to either (1) receive full repayment of the note outstanding or (2) convert the entire outstanding amount of principal and accrued interest into shares of Series F preferred stock at a price per share of $3.8590. The outstanding balance of principal and accrued interest automatically converts into fully paid and nonassessable shares of preferred stock issued on the issuance of preferred stock with aggregate gross proceeds of at least $25.0 million (a “Qualified Financing”) prior to the maturity date of the convertible notes. On the issuance of preferred stock with aggregate gross proceeds of less than $25.0 million (a “Non-Qualified Financing”), holders of the Convertible Notes could elect to convert all or any portion of the outstanding principal and interest into fully paid and nonassessable shares of preferred stock. On conversion of the convertible notes in either a Qualified Financing or Non-Qualified Financing, preferred shares would be issued at a price of 90% of the price per share paid by the purchasers of preferred stock participating in the financing. The Qualified Financing and Non-Qualified Financing redemption features were determined to be a compound embedded derivative requiring bifurcation and separate accounting at its estimated fair value. On issuance of the Convertible Notes, the Company recognized a liability of $0.4 million for the estimated fair value of the embedded derivative and incurred $0.1 million in debt issuance costs, both of which were recorded as a debt discount associated with the Convertible Notes. In June 2018, the outstanding balance of principal and accrued interest on the Convertible Notes of $14.6 million converted into 1,067,550 and 1,997,709 shares of the Company’s Series G redeemable convertible and convertible preferred stock, respectively, at a price of $4.7565 per share in conjunction with the Company’s Series G convertible preferred stock financing, which was a Qualified Financing under the terms of the Convertible Notes. The conversion of the Convertible Notes into Series G redeemable convertible preferred stock and Series G convertible preferred stock was accounted for as an extinguishment. The extinguishment of the Convertible Notes was considered a capital transaction and accordingly, the Company recognized a $0.4 million loss on extinguishment through additional paid in capital equal to the unamortized debt discount at the date of conversion. During the nine months ended September 30, 2018 the Company recognized

Convertible Preferred Stock and

Convertible Preferred Stock and Redeemable Convertible Preferred Stock	9 Months Ended
	Sep. 30, 2019
Temporary Equity Disclosure [Abstract]
Convertible Preferred Stock and Redeemable Convertible Preferred Stock	Note 8. Convertible Preferred Stock and Redeemable Convertible Preferred Stock On July 2, 2019 and immediately prior to the completion of the IPO, all outstanding shares of convertible preferred stock and redeemable convertible preferred stock then outstanding converted into 58,363,606 shares of common stock. The carrying value of the redeemable convertible preferred stock was accreted to redemption value from the date of issuance to the earliest redemption date using the effective interest method. The Company determined that redemption of the redeemable convertible preferred stock was not probable and as such, did not record any additional accretion after March 31, 2019. At December 31, 2018, convertible preferred stock and redeemable convertible preferred stock consisted of the following (in thousands, except share amounts): December 31, 2018 Shares Authorized Shares Issued and Outstanding Net Carrying Value Aggregate Liquidation Preference Series A 18,960,000 18,941,619 $ 9,161 $ 9,217 Series B 13,784,443 13,652,791 13,774 14,000 Series C 9,335,659 9,328,791 20,289 20,374 Series D 14,367,652 14,324,642 39,886 40,000 Series E 13,612,543 13,586,946 39,880 40,000 Series F 12,956,724 12,956,724 54,968 57,211 Series G 21,986,733 21,986,733 116,242 120,544 Total 105,003,754 104,778,246 $ 294,200 $ 301,346

Share-based Compensation Plans

Share-based Compensation Plans	9 Months Ended
	Sep. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-based Compensation Plans	Note 9. Share-based Compensation Plans 2011 Equity Incentive Plan In 2011, the Company adopted the Equity Incentive Plan (2011 Plan) authorizing the granting of incentive stock options (ISOs) and non-statutory stock options (NSOs) to eligible participants for up to 12,987,255 shares of common stock. Under the 2011 Plan, incentive stock options and non-statutory stock options are to be granted at an exercise price that is no less than 100% of the fair value of the stock at the date of grant. Options generally vest over four years and are exercisable for up to 10 years after the date of grant. Incentive stock options granted to stockholders who own more than 10% of the outstanding stock of the Company at the time of grant must be issued at an exercise price no less than 110% of the fair value of the stock on the date of grant. The 2011 Plan has been replaced by the Company’s 2019 Plan as defined below with respect to future equity awards. 2019 Equity Incentive Plan In connection with the Company’s initial public offering, the Company adopted the 2019 Equity Incentive Plan (the “2019 Plan”). The 2019 Plan allows the Company to grant stock options, stock appreciation rights, restricted stock, restricted stock units and performance awards to participants. Subject to the terms and conditions of the 2019 Plan, the initial number of shares authorized for grants under the 2019 Plan is 8,000,000. Employee Stock Purchase Plan In connection with the Company’s initial public offering, the Company adopted the Employee Stock Purchase Plan. The Employee Stock Purchase Plan permits employees to purchase shares of common stock during six-month offering periods at a purchase price equal to the lesser of (1) 85% of the fair market value of a share of common stock on the first business day of such offering period and (2) 85% of the fair market value of a share of common stock on the last business day of such offering period. Stock-based Compensation Total stock-based compensation expense, excluding compensation expense related to stock sales by current and former employees, by function was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Marketing $ 145 $ 42 $ 287 $ 115 Operations and technology 1,098 239 2,064 775 Selling, general and administrative 1,277 459 2,565 1,076 Total $ 2,520 $ 740 $ 4,916 $ 1,966 The amounts presented in the above table exclude compensation expense related to the stock sales by current and former employees. In September 2018, executives of the Company sold an aggregate of 432,270 shares of the Company’s common stock at a price of $9.0902 per share for an aggregate amount of $3.9 million to certain of the Company’s existing investors. The Company determined that the purchase price was in excess of the fair value of such shares. As a result, during the year ended December 31, 2018, the Company recorded the excess of the purchase price above fair value of $0.8 million as compensation expense within selling, general and administrative in the statements of operations and a corresponding credit to additional paid-in capital. Additionally , in March 2019, executives of the Company sold an aggregate of 382,477 shares of the Company’s common stock at a price of $12.72 per share for an aggregate amount of $4.9 million to certain of the Company’s existing investors. The Company determined that the purchase price was in excess of the fair value of such shares. As a result, during the three months ended March 31, 2019, the Company recorded the excess of the purchase price above fair value of $0.8 million as compensation expense within selling, general and administrative in the statement of operations and a corresponding credit to additional paid-in capital.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 10. Commitments and Contingencies Leases The Company leases its corporate offices, retail spaces and merchandising and fulfillment facilities under various noncancelable operating leases with terms ranging from one year to eleven years. Rent expense from operating leases totaled $4.8 million and $2.7 million for the three months ended September 30, 2019 and 2018, respectively and $13.4 million and $6.9 million for the nine months ended September 30, 2019 and 2018, respectively. The current portion of deferred rent was $0.8 million as of September 30, 2019 and is included in other accrued and current liabilities on the balance sheets. The noncurrent portion of deferred rent was $6.8 million as of September 30, 2019 and is included in other noncurrent liabilities on the balance sheets. As of September 30, 2019, the Company’s future minimum lease payments under the noncancelable leases are as follows (in thousands): Year Ending December 31, Operating Leases 2019 $ 4,728 2020 19,439 2021 19,455 2022 16,733 2023 15,539 Thereafter 64,537 Total future minimum payments $ 140,431 Noncancelable Purchase Commitments The Company has commitments for cloud services and other items in the ordinary course of business with varying expiration terms through 2021. As of September 30, 2019, there were no material changes to the Company’s noncancelable purchase commitments disclosed in the financial statements in the Prospectus. Other Commitments In January 2018, the Company and the University of Arizona Foundation entered into an endowment agreement (the “Endowment Agreement”) to establish a fund (the “Fund”) to create and grow a gemology degree program in the Department of Geosciences at the University of Arizona (the “University”). The Company agreed to donate a total of $2.0 million, payable in four annual installments of $0.5 million. The first installment was paid in January 2018 on execution of the Endowment Agreement. There are no conditions that the University must meet to receive the funds nor any penalties to the University for nonperformance. The Endowment Agreement directs the use of the funds but contains no binding restrictions on the use of the funds. On the execution of the Endowment Agreement, the Company recognized $1.7 million expense for the estimated fair value of the grant, using a discount rate of 10%, to selling, general and administrative expenses in the statements of operations. The Company recognized a corresponding liability for the remaining installment payments and will recognize accretion of the liability as interest expense over the remaining term of the Endowment Agreement. Interest expense related to the accretion of the grant liability was not material in the three and nine months ended September 30, 2019 and 2018. As of September 30, 2019, the outstanding liability was $0.9 million, of which $0.4 million is included in other accrued and current liabilities on the balance sheets and $0.5 million is included in other noncurrent liabilities on the balance sheets. Contingencies From time to time the Company is subject to, and it is presently involved in, litigation and other legal proceedings. Accounting for contingencies requires the Company to use judgment related to both the likelihood of a loss and the estimate of the amount or range of loss. The Company records a loss contingency when it is probable that a liability has been incurred and the amount of the loss can be reasonably estimated. The Company discloses material contingencies when a loss is not probable but reasonably possible. On November 14, 2018, Chanel, Inc. (“Chanel”) filed a lawsuit against the Company in the U.S. District Court for the Southern District of New York bringing various trademark and advertising-related claims under the Lanham Act and New York state law analogues. Chanel alleges, among other things, that the Company has misrepresented certain counterfeit Chanel products as authentic Chanel products, that the Company’s resale of Chanel products confuses consumers into believing that Chanel is affiliated with the Company and involved in authenticating consignors ’ ’ On September 11, 2019, a purported shareholder class action complaint was filed against the Company, its officers and directors and the underwriters of its IPO in the Superior Court of the State of California in the County of San Mateo. A second purported class action was filed in Marin County Superior Court on September 16, 2019 and a third purported action was filed in Marin County Superior Court on October 7, 2019. The complaints each allege claims under the Securities Act of 1933 , as amended (“Securities Act”) on behalf of a purported class of those who acquired the Company’s stock pursuant to or traceable to the registration statement for the Company’s IPO. The complaints allege, among other things, that the defendants violated federal securities laws by issuing false or misleading statements regarding certain of the Company’s key financial and operating metrics at the time of the IPO. The complaints seek, among other things, damages and interest, rescission, and attorneys’ fees and costs. Plaintiff in the San Mateo action voluntarily dismissed that case in order to re-file in Marin County Superior Court and the cases are in the process of being coordinated before the Marin County Superior Court. While the Company intends to vigorously defend against this consolidated litigation, the cases are at a very early stage and there can be no assurance that the Company will be successful in its defense. For this same reason, the Company cannot currently estimate the loss or the range of possible losses it may experience in connection with this litigation. Indemnifications In the ordinary course of business, the Company may provide indemnifications of varying scope and terms to vendors, directors, officers and other parties with respect to certain matters. The Company has not incurred any material costs as a result of such indemnifications and have not accrued any liabilities related to such obligations in its financial statements.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Note 11. Income Taxes The quarterly income tax provision reflects an estimate of the corresponding quarter’s state taxes in the United States.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Net Loss Per Share	Note 12. Net Loss Per Share A reconciliation of the numerator and denominator used in the calculation of the basic and diluted net loss per share attributable to common stockholders is as follows (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Numerator Net loss attributable to common stockholders $ (25,274 ) $ (25,085 ) $ (78,726 ) $ (59,237 ) Denominator Weighted-average common shares outstanding used to calculate net loss per share attributable to common stockholders, basic and diluted 84,634,956 8,349,403 34,556,485 8,321,296 Net loss per share attributable to common stockholders, basic and diluted $ (0.30 ) $ (3.00 ) $ (2.28 ) $ (7.12 ) The following securities 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 (on an as-converted basis): September 30, 2019 2018 Convertible preferred stock — 36,862,298 Redeemable convertible preferred stock — 16,410,256 Options to purchase common stock 9,417,490 8,628,662 Restricted stock units 551,549 — Warrants to purchase convertible preferred stock — 103,563 Warrant to purchase common stock — 67,974 Total 9,969,039 62,072,753

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of expenses during the reporting period. Significant items subject to such estimates and assumptions include those related to revenue recognition, including the returns reserve and material right related to the Company’s tiered consignor commission plan, valuation of inventory, stock-based compensation, redemption value of redeemable convertible preferred stock, and other contingencies. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could differ from those estimates.
Net Loss per Share Attributable to Common Stockholders	Net Loss per Share Attributable to Common Stockholders The Company follows the two-class method when computing net loss per common share when shares are issued that meet the definition of participating securities. The two-class method determines net loss per common share for each class of common stock and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to common stockholders for the period to be allocated between common stock and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed. The Company’s redeemable convertible preferred stock and convertible preferred stock contractually entitles the holders of such shares to participate in dividends but does not contractually require the holders of such shares to participate in the Company’s losses. For periods in which the Company reports net losses, diluted net loss per common share attributable to common stockholders is the same as basic net loss per common share attributable to common stockholders, because potentially dilutive common shares are not assumed to have been issued if their effect is anti-dilutive.
Revenue Recognition	Revenue Recognition The Company generates revenue from the sale of pre-owned luxury goods through its online marketplace. Consignment and Service Revenue The Company provides a service to sell pre-owned luxury goods on behalf of consignors to buyers through its online marketplace and retail locations. The Company retains a percentage of the proceeds received as payment for its consignment service, which the Company refers to as its take rate. The Company reports consignment revenue on a net basis as an agent and not the gross amount collected from the buyer. Title to the consigned goods remain with the consignor until transferred to the end customer subsequent to purchase of the consigned goods. The Company does not take title of consigned goods at any time except in certain cases where returned goods become Company-owned inventory. The Company recognizes consignment revenue upon purchase of the consigned good by the buyer as its performance obligation of providing consignment services to the consignor is satisfied at that point. Consignment revenue is recognized net of certain buyer incentives and estimated returns and cancellations. The Company recognizes a returns reserve, based on historical experience, which is recorded in other accrued and current liabilities on the balance sheets (see Note 5). Sales tax assessed by governmental authorities is excluded from revenue. Certain transactions provide consignors with a material right resulting from the tiered consignor commission plan. Under this plan, the amount an individual consignor receives for future sales of consigned goods may be dependent on previous consignment sales for that consignor within his/her consignment period. Accordingly, in certain consignment transactions, a small portion of the Company’s consignment revenue is allocated to such material right using the portfolio method and recorded as deferred revenue. The Company charges shipping fees to buyers and has elected to treat shipping and handling activities performed after control transfers to the buyer as fulfillment activities. All outbound shipping and handling costs are accounted for as fulfillment costs in cost of consignment and service revenue at the time revenue is recognized. The Company also generates subscription revenue from monthly memberships allowing buyers early access to shop for luxury goods. The buyers receive the early access and other benefits over the term of the subscription period, which represents a single stand-ready performance obligation. Therefore, the subscription fees paid by the buyer are recognized over the monthly subscription period. Subscription revenue was not material in the three or nine months ended September 30, 2019 and 2018. Direct Revenue The Company generates direct revenue from the sale of Company-owned inventory. The Company recognizes direct revenue upon shipment of the purchased good to the buyer as its performance obligation, consisting of the sale of goods, is satisfied at this point. Direct revenue is recognized net of incentives and estimated returns. Sales tax assessed by governmental authorities is excluded from revenue. Incentives Promotional incentives, which include basket promotional code discounts and other credits, may periodically be offered to consignors and buyers. These are treated as a reduction of consignment and service revenue and direct revenue. Additionally, the Company may offer site credits to buyers on current transactions to be applied towards future transactions, which are accounted as site credit liabilities and included in other accrued and current liabilities on the balance sheets. Contract Liabilities The Company’s contractual liabilities consist of deferred revenue for material rights primarily related to the tiered consignor commission plan totaling $3.4 million as of September 30, 2019 and
Cost of Revenue	Cost of Revenue Cost of revenue for consignment and services and direct revenue consist of shipping costs, credit card fees, packaging, customer service and website hosting services. Cost of direct revenue also includes the cost of goods sold.
Stock-based Compensation	Stock-based Compensation Stock-based compensation expense related to employees is measured based on the grant-date fair value of the awards. Compensation expense is recognized in the statements of operations over the period during which the employee is required to perform services in exchange for the award (the vesting period of the applicable award) using the straight-line method. The Company estimates the fair value of stock options granted using the Black-Scholes option pricing model and accounts for forfeitures as they occur. The fair value of restricted stock units (“RSUs”) is estimated based on the fair market value of the Company’s common stock on the date of grant, which is determined based on the closing price of the Company’s common stock. Historically, certain employees were able to sell their shares of the Company’s common stock to the Company’s existing investors. In such secondary sale transactions, the Company recorded the difference in purchase price and the fair value of such shares as compensation expense within selling, general and administrative in the statement of operations and a corresponding credit to additional paid-in capital.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments purchased with original maturities of three months or less from the purchase date to be cash equivalents. Cash equivalents consist primarily of amounts invested in reverse repurchase agreement (“RRAs”). RRAs are collateralized by deposits in the form of United States government securities and obligations for an amount not less than 102% of their value. The Company has a policy that the collateral has at least an A (or equivalent) credit rating. The Company utilizes a third-party custodian to manage the exchange of funds and ensure that collateral received is maintained at 102% of the value of the RRAs on a daily basis. RRAs with stated maturities of greater than three months from the date of purchase are classified as short-term investments. Restricted cash consists of cash deposited with a financial institution as collateral for the Company’s letters of credit for its facility leases and the Company’s credit cards. As of September 30, 2019 and December 31, 2018, the Company had letters of credit outstanding and collateral accounts in the amounts of zero and $11.2 million, respectively. The following table provides a reconciliation of cash, cash equivalents and restricted cash that sum to the total of the same amounts shown in the statements of cash flows (in thousands): September 30, 2019 September 30, 2018 Cash and cash equivalents $ 364,995 $ 54,704 Restricted cash — 11,234 Total cash, cash equivalents and restricted cash $ 364,995 $ 65,938
Inventory, Net	Inventory, Net Inventory primarily consists of finished goods arising from goods returned after the consignor has been paid, upon which the Company assumes the title to the goods until it is resold and recognizes it as inventory in an amount equal to that paid to the consignor. The Company also periodically purchases finished goods directly from vendors. Inventory is valued at the lower of cost and net realizable value using the specific identification method and the Company records provisions, as appropriate, to write down obsolete and excess inventory to estimated net realizable value. After the inventory value is reduced, adjustments are not made to increase it from the estimated net realizable value. The inventory reserve, which reduces inventory on the balance sheets, was $1.4 million and $0.7 million as of September 30, 2019 and December 31, 2018, respectively.
Software Development Costs	Software Development Costs Proprietary software includes the costs of developing the Company’s internal proprietary business platform. The Company capitalizes qualifying proprietary software development costs that are incurred during the application development stage. Capitalization of costs begins when two criteria are met: (1) the preliminary project stage is completed and (2) it is probable that the software will be completed and used for its intended function. Such costs are capitalized in the period incurred. Capitalization ceases and amortization begins when the software is substantially complete and ready for its intended use, including the completion of all significant testing. Costs related to preliminary project activities and post-implementation operating activities are expensed as incurred.
Accretion of Redeemable Convertible Preferred Stock	Accretion of Redeemable Convertible Preferred Stock The carrying value of the redeemable convertible preferred stock that is probable of redemption is accreted to redemption value from the date of issuance to the earliest redemption date using the effective interest method. Increases to the carrying value of redeemable convertible preferred stock recognized in each period are charged to additional paid-in capital, or in the absence of additional paid-in capital, charged to accumulated deficit.
Convertible Preferred Stock Warrant Liability	Convertible Preferred Stock Warrant Liability The Company issued convertible preferred stock warrants in conjunction with the issuance of debt. Such warrants were recorded as other noncurrent liabilities on the balance sheets at their estimated fair value because the shares underlying the warrants may obligate the Company to transfer assets to the holders at a future date under certain circumstances such as a deemed liquidation event. The warrants are subject to re-measurement at each balance sheet date and the change in fair value, if any, is included in other expense, net. The Company continued to remeasure these warrants until the earlier of the expiration, exercise or conversion of the convertible preferred stock warrants into common warrants, which occurred upon the completion of the IPO on July 2, 2019. In connection with the completion of the IPO, the convertible preferred stock warrants automatically converted into common stock warrants. Upon conversion of the convertible preferred stock warrants, the related convertible preferred stock warrant liability was reclassified to additional paid-in capital.
Leases	Leases Leases are reviewed for classification as operating or capital leases. For operating leases, the Company recognizes rent on a straight-line basis over the term of the lease. The Company records the difference between cash payments and rent expense recognized as a deferred rent liability included in other accrued and current liabilities and other noncurrent liabilities on the balance sheets. Incentives granted under the Company’s facility leases, including allowances to fund leasehold improvements, are deferred and are recognized as adjustments to rental expense on a straight-line basis over the term of the lease.
Concentrations of Credit Risks	Concentrations of Credit Risks Financial instruments that potentially subject the Company to concentrations of credit risk consist of cash and cash equivalents. At times, such amount may exceed federally-insured limits. The Company reduces credit risk by placing its cash and cash equivalents with major credit-worthy financial institutions within the United States. As of September 30, 2019 and December 31, 2018, there were no customers that represented 10% or more of the Company’s accounts receivable balance and there were no customers that individually exceeded 10% of the Company’s total revenue for each of the three and nine months ended September 30, 2019 and 2018.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers In June 2018, the FASB issued ASU 2018-08, Clarifying the Scope and the Accounting Guidance for Contributions Received and Contributions Made (Topic 958) In August 2018, the FASB issued ASU 2018-15 , Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40)
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In January 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities (Subtopic 825-10) fiscal years beginning after December 15, 2018, and interim periods within fiscal years beginning after December 15, 2019 In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments (Topic 326) The Company does not expect the adoption of this standard to have a material impact on the operating results. In June 2018, the FASB issued ASU 2018-07, Compensation—Stock Compensation (Topic 718), In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820)

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash that sum to the total of the same amounts shown in the statements of cash flows (in thousands): September 30, 2019 September 30, 2018 Cash and cash equivalents $ 364,995 $ 54,704 Restricted cash — 11,234 Total cash, cash equivalents and restricted cash $ 364,995 $ 65,938

Cash, Cash Equivalents and Sh_2

Cash, Cash Equivalents and Short Term Investments (Tables)	9 Months Ended
	Sep. 30, 2019
Cash And Cash Equivalents [Abstract]
Summary of Estimated Value of Cash, Cash Equivalents and Short Term Investments	The following tables summarize the estimated value of the Company’s cash, cash equivalents and short-term investments (in thousands): September 30, 2019 Amortized Cost Unrealized Gain Unrealized Loss Fair Value Cash and cash equivalents: Cash $ 119,130 $ — $ — $ 119,130 Money market fund 231,865 — — 231,865 Corporate bonds 2,000 — — 2,000 Reverse repurchase agreements 12,000 — — 12,000 Total cash and cash equivalents $ 364,995 $ — $ — $ 364,995 Short-term investments: U.S. corporate bonds $ 2,282 $ 1 — $ 2,283 International corporate bonds 3,007 — — 3,007 Total short-term investments $ 5,289 $ 1 $ — $ 5,290 December 31, 2018 Amortized Cost Unrealized Gain Unrealized Loss Fair Value Cash and cash equivalents: Cash $ 10,253 $ — $ — $ 10,253 Money market fund 140 — — 140 Reverse repurchase agreements 24,000 — — 24,000 Total cash and cash equivalents $ 34,393 $ — $ — $ 34,393 Short-term investments: U.S. corporate bonds $ 21,184 $ — $ (19 ) $ 21,165 International corporate bonds 5,972 — (6 ) 5,966 Total short-term investments $ 27,156 $ — $ (25 ) $ 27,131

Fair Value Measurement (Tables)

Fair Value Measurement (Tables)	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Schedule of Financial Instruments Measured at Fair Value	The following tables provide the financial instruments measured at fair value (in thousands): September 30, 2019 Level 1 Level 2 Level 3 Total Assets Cash equivalents: Money market fund $ 231,865 $ — $ — $ 231,865 Corporate bonds — 2,000 — 2,000 Reverse repurchase agreements — 12,000 — 12,000 Total cash equivalents $ 231,865 $ 14,000 $ — $ 245,865 Short-term investments: U.S. corporate bonds $ — $ 2,283 $ — $ 2,283 International corporate bonds — 3,007 — 3,007 Total short-term investments $ — $ 5,290 $ — $ 5,290 Total assets $ 231,865 $ 19,290 $ — $ 251,155 December 31, 2018 Level 1 Level 2 Level 3 Total Assets Cash equivalents: Money market fund $ 140 $ — $ — $ 140 Reverse repurchase agreements — 24,000 — 24,000 Total cash equivalents $ 140 $ 24,000 $ — $ 24,140 Short-term investments: U.S. corporate bonds $ — $ 21,165 $ — $ 21,165 International corporate bonds — 5,966 — 5,966 Total short-term investments $ — $ 27,131 $ — $ 27,131 Total assets $ 140 $ 51,131 $ — $ 51,271 Liabilities Convertible preferred stock warrant liability $ — $ — $ 610 $ 610 Total liabilities $ — $ — $ 610 $ 610
Schedule of Fair Value of Level 3 Liabilities Recorded	The following table presents a rollforward of the fair value of the level 3 liabilities recorded at fair value at September 30, 2019 (in thousands): Convertible Preferred Stock Warrant Liability Balance as of December 31, 2018 $ 610 Changes in estimated fair value 2,100 Reclass to additional paid-in capital upon conversion to common stock warrants (2,710 ) Balance as of September 30, 2019 $ —

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 30, 2019
Balance Sheet Related Disclosures [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consists of the following (in thousands): September 30, 2019 December 31, 2018 Proprietary software $ 20,721 $ 14,052 Furniture and equipment 18,463 12,665 Automobiles 521 346 Leasehold improvements 34,954 25,702 74,659 52,765 Less: accumulated depreciation and amortization (28,944 ) (19,479 ) Property and equipment, net $ 45,715 $ 33,286
Schedule of Other Accrued and Current Liabilities	Other accrued and current liabilities consist of the following (in thousands): September 30, 2019 December 31, 2018 Returns reserve $ 12,163 $ 14,311 Accrued compensation 8,134 8,078 Site credit liability 5,612 4,700 Accrued sales tax and other taxes 4,703 4,476 Deferred revenue 3,582 3,184 Accrued marketing and outside services 4,963 4,152 Other 3,391 3,055 Other accrued and current liabilities $ 42,548 $ 41,956

Convertible Preferred Stock a_2

Convertible Preferred Stock and Redeemable Convertible Preferred Stock (Tables)	9 Months Ended
	Sep. 30, 2019
Temporary Equity Disclosure [Abstract]
Summary of Convertible Preferred Stock and Redeemable Convertible Preferred Stock	At December 31, 2018, convertible preferred stock and redeemable convertible preferred stock consisted of the following (in thousands, except share amounts): December 31, 2018 Shares Authorized Shares Issued and Outstanding Net Carrying Value Aggregate Liquidation Preference Series A 18,960,000 18,941,619 $ 9,161 $ 9,217 Series B 13,784,443 13,652,791 13,774 14,000 Series C 9,335,659 9,328,791 20,289 20,374 Series D 14,367,652 14,324,642 39,886 40,000 Series E 13,612,543 13,586,946 39,880 40,000 Series F 12,956,724 12,956,724 54,968 57,211 Series G 21,986,733 21,986,733 116,242 120,544 Total 105,003,754 104,778,246 $ 294,200 $ 301,346

Share-based Compensation Plans

Share-based Compensation Plans (Tables)	9 Months Ended
	Sep. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Total Stock-based Compensation Expense, Excluding Compensation Expense Related to Stock Sales, by Function	Total stock-based compensation expense, excluding compensation expense related to stock sales by current and former employees, by function was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Marketing $ 145 $ 42 $ 287 $ 115 Operations and technology 1,098 239 2,064 775 Selling, general and administrative 1,277 459 2,565 1,076 Total $ 2,520 $ 740 $ 4,916 $ 1,966

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Schedule of Future Minimum Lease Payments Under Noncancelable Operating Leases	As of September 30, 2019, the Company’s future minimum lease payments under the noncancelable leases are as follows (in thousands): Year Ending December 31, Operating Leases 2019 $ 4,728 2020 19,439 2021 19,455 2022 16,733 2023 15,539 Thereafter 64,537 Total future minimum payments $ 140,431

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Schedule of Reconciliation of Numerator and Denominator Used in Calculation of Basic and Diluted Net Loss Per Share	A reconciliation of the numerator and denominator used in the calculation of the basic and diluted net loss per share attributable to common stockholders is as follows (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Numerator Net loss attributable to common stockholders $ (25,274 ) $ (25,085 ) $ (78,726 ) $ (59,237 ) Denominator Weighted-average common shares outstanding used to calculate net loss per share attributable to common stockholders, basic and diluted 84,634,956 8,349,403 34,556,485 8,321,296 Net loss per share attributable to common stockholders, basic and diluted $ (0.30 ) $ (3.00 ) $ (2.28 ) $ (7.12 )
Schedule of Anti-dilutive Securities Excluded from Computation of Diluted Net Loss Per Share	The following securities 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 (on an as-converted basis): September 30, 2019 2018 Convertible preferred stock — 36,862,298 Redeemable convertible preferred stock — 16,410,256 Options to purchase common stock 9,417,490 8,628,662 Restricted stock units 551,549 — Warrants to purchase convertible preferred stock — 103,563 Warrant to purchase common stock — 67,974 Total 9,969,039 62,072,753

Description of Business and B_2

Description of Business and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Millions	Jul. 02, 2019USD ($)$ / sharesshares	Sep. 30, 2019shares	Dec. 31, 2018shares
Class Of Stock [Line Items]
Common stock, shares authorized		500,000,000	145,467,774
Redeemable convertible preferred stock outstanding			104,778,246
Initial Public Offering
Class Of Stock [Line Items]
Number of common stock issued	15,000,000
Common stock issued price per share | $ / shares	$ 20
Net proceeds from issuance of initial public offering | $	$ 315.5
Underwriting discounts and commissions | $	24.1
Issuance costs | $	$ 5.4
Common stock, shares authorized	500,000,000
Undesignated preferred stock, shares authorized for issuance	50,000,000
Redeemable convertible preferred stock outstanding	114,960,357
Convertible preferred stock converted into common stock	58,363,606
Description of reverse stock split		On June 13, 2019 the Company effected a reverse split of shares of the Company’s common stock on a 1-for-2 basis
Reverse stock split ratio		0.5
Initial Public Offering | Common Stock Warrants
Class Of Stock [Line Items]
Conversion of preferred stock warrants into common stock warrants	103,563
Underwriters' Option to Purchase Additional Shares
Class Of Stock [Line Items]
Number of common stock issued	2,250,000
Common stock issued price per share | $ / shares	$ 20

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019USD ($)Customer	Sep. 30, 2018Customer	Sep. 30, 2019USD ($)Customer	Sep. 30, 2018Customer	Dec. 31, 2018USD ($)Customer
Summary Of Significant Accounting Policies [Line Items]
Contractual liabilities	$ 3,582		$ 3,582		$ 3,184
Percentage of reverse repurchase agreement collateralized received	102.00%		102.00%
Letters of credit outstanding and collateral amount	$ 0		$ 0		11,200
Inventory reserve	$ 1,400		$ 1,400		$ 700
Accounts Receivable
Summary Of Significant Accounting Policies [Line Items]
Number of major customers | Customer			0		0
Total Revenue
Summary Of Significant Accounting Policies [Line Items]
Number of major customers | Customer	0	0	0	0
Maximum
Summary Of Significant Accounting Policies [Line Items]
Percentage of reverse repurchase agreement collateralized deposits	102.00%		102.00%
Deferred Revenue
Summary Of Significant Accounting Policies [Line Items]
Contractual liabilities	$ 3,400		$ 3,400		$ 2,700

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Cash and cash equivalents	$ 364,995	$ 34,393	$ 54,704
Restricted cash			11,234
Total cash, cash equivalents and restricted cash	$ 364,995	$ 45,627	$ 65,938	$ 20,660

Cash, Cash Equivalents and Sh_3

Cash, Cash Equivalents and Short-Term Investments - Summary of Estimated Value of Cash, Cash Equivalents and Short-term Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents, amortized cost	$ 364,995	$ 34,393	$ 54,704
Cash and cash equivalents, fair value	364,995	34,393
Short-term investments, amortized cost	5,289	27,156
Short-term investments, unrealized gain	1
Short-term investments, unrealized loss		(25)
Short-term investments, fair value	5,290	27,131
Cash
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents, amortized cost	119,130	10,253
Cash and cash equivalents, fair value	119,130	10,253
Money Market Fund
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents, amortized cost	231,865	140
Cash and cash equivalents, fair value	231,865	140
Corporate Bonds
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents, amortized cost	2,000
Cash and cash equivalents, fair value	2,000
Reverse Repurchase Agreements
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents, amortized cost	12,000	24,000
Cash and cash equivalents, fair value	12,000	24,000
U.S. Corporate Bonds
Cash And Cash Equivalents [Line Items]
Short-term investments, amortized cost	2,282	21,184
Short-term investments, unrealized gain	1
Short-term investments, unrealized loss		(19)
Short-term investments, fair value	2,283	21,165
International Corporate Bonds
Cash And Cash Equivalents [Line Items]
Short-term investments, amortized cost	3,007	5,972
Short-term investments, unrealized loss		(6)
Short-term investments, fair value	$ 3,007	$ 5,966

Cash, Cash Equivalents and Sh_4

Cash, Cash Equivalents and Short-Term Investments - Additional Information (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Maximum
Cash And Cash Equivalents [Line Items]
Short term investments contractual maturity term	1 year	1 year

Fair Value Measurement - Additi

Fair Value Measurement - Additional Information (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Asset transfers Level 1 to Level 2	$ 0	$ 0
Asset transfers Level 2 to Level 1	0	0
Asset transfers into Level 3	0	0
Asset transfers out of Level 3	0	0
Liabilities transfers Level 1 to Level 2	0	0
Liabilities transfers Level 2 to Level 1	0	0
Liability transfers into Level 3	0	0
Liability transfers out of Level 3	$ 0	$ 0

Fair Value Measurement - Schedu

Fair Value Measurement - Schedule of Financial Instruments Measured at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Assets
Cash equivalents	$ 364,995	$ 34,393
Short-term investments	5,290	27,131
Recurring
Assets
Cash equivalents	245,865	24,140
Short-term investments	5,290	27,131
Total assets	251,155	51,271
Liabilities
Total liabilities		610
Recurring | Convertible Preferred Stock Warrant Liability
Liabilities
Total liabilities		610
Recurring | Money Market Fund
Assets
Cash equivalents	231,865	140
Recurring | Corporate Bonds
Assets
Cash equivalents	2,000
Recurring | Reverse Repurchase Agreements
Assets
Cash equivalents	12,000	24,000
Recurring | U.S. Corporate Bonds
Assets
Short-term investments	2,283	21,165
Recurring | International Corporate Bonds
Assets
Short-term investments	3,007	5,966
Recurring | Level 1
Assets
Cash equivalents	231,865	140
Total assets	231,865	140
Recurring | Level 1 | Money Market Fund
Assets
Cash equivalents	231,865	140
Recurring | Level 2
Assets
Cash equivalents	14,000	24,000
Short-term investments	5,290	27,131
Total assets	19,290	51,131
Recurring | Level 2 | Corporate Bonds
Assets
Cash equivalents	2,000
Recurring | Level 2 | Reverse Repurchase Agreements
Assets
Cash equivalents	12,000	24,000
Recurring | Level 2 | U.S. Corporate Bonds
Assets
Short-term investments	2,283	21,165
Recurring | Level 2 | International Corporate Bonds
Assets
Short-term investments	$ 3,007	5,966
Recurring | Level 3
Liabilities
Total liabilities		610
Recurring | Level 3 | Convertible Preferred Stock Warrant Liability
Liabilities
Total liabilities		$ 610

Fair Value Measurement - Sche_2

Fair Value Measurement - Schedule of Fair Value of Level 3 Liabilities Recorded (Details) - Convertible Preferred Stock Warrant Liability $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 610
Changes in estimated fair value	2,100
Reclass to additional paid-in capital upon conversion to common stock warrants	$ (2,710)

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 74,659	$ 52,765
Less: accumulated depreciation and amortization	(28,944)	(19,479)
Property and equipment, net	45,715	33,286
Proprietary Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	20,721	14,052
Furniture And Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	18,463	12,665
Automobiles
Property Plant And Equipment [Line Items]
Property and equipment, gross	521	346
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 34,954	$ 25,702

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Property Plant And Equipment [Abstract]
Depreciation and amortization expense on property and equipment	$ 3.5	$ 2.4	$ 9.5	$ 6.5

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Other Accrued and Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Returns reserve	$ 12,163	$ 14,311
Accrued compensation	8,134	8,078
Site credit liability	5,612	4,700
Accrued sales tax and other taxes	4,703	4,476
Deferred revenue	3,582	3,184
Accrued marketing and outside services	4,963	4,152
Other	3,391	3,055
Other accrued and current liabilities	$ 42,548	$ 41,956

Debt and Convertible Preferre_2

Debt and Convertible Preferred Stock Warrants - Additional Information (Details) - USD ($)	Jul. 26, 2019	Jul. 31, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2013
Debt Disclosure [Line Items]
Interest expense related to term loans				$ 100,000	$ 200,000		$ 600,000	$ 500,000
Warrants outstanding				0			0
Letter of Credit
Debt Disclosure [Line Items]
Deb maturity date									Aug. 1, 2019
Line of credit									$ 1,500,000
IPO
Debt Disclosure [Line Items]
Debt, success fee		$ 300,000
Series G Convertible Preferred Stock
Debt Disclosure [Line Items]
Debt, success fee			$ 100,000
Series B Convertible Preferred Stock
Debt Disclosure [Line Items]
Outstanding preferred stock warrants exercised (in shares)				131,652			131,652
Exercise price of warrants (in dollars per share)				$ 1.03			$ 1.03
Series C Convertible Preferred Stock
Debt Disclosure [Line Items]
Outstanding preferred stock warrants exercised (in shares)				6,868			6,868
Exercise price of warrants (in dollars per share)				$ 2.18			$ 2.18
Series D Convertible Preferred Stock
Debt Disclosure [Line Items]
Outstanding preferred stock warrants exercised (in shares)				43,010			43,010
Exercise price of warrants (in dollars per share)				$ 2.79			$ 2.79
Series E Convertible Preferred Stock
Debt Disclosure [Line Items]
Outstanding preferred stock warrants exercised (in shares)				25,597			25,597
Exercise price of warrants (in dollars per share)				$ 2.93			$ 2.93
Convertible Preferred Stock
Debt Disclosure [Line Items]
Warrant term							10 years
Term Loan Facility
Debt Disclosure [Line Items]
Maximum borrowing capacity											$ 5,000,000
Increase in borrowing capacity							$ 11,600,000
Debt instrument required covenants percentage on forecasted gross revenue							80.00%
Debt, combined success fee									$ 300,000
Debt, additional success fee						$ 100,000
Net cash proceeds from subordinated debt securities						$ 50,000,000
Term Loans
Debt Disclosure [Line Items]
Long-term debt, gross										$ 15,000,000
Repayments on loans	$ 6,500,000
Term Loan I
Debt Disclosure [Line Items]
Long-term debt, gross										$ 7,500,000
Deb maturity date									Jan. 31, 2021	Jan. 31, 2019
Number of equal monthly installments							30 equal monthly installments
Variable annual interest rate									0.35%	0.10%
Term Loan II
Debt Disclosure [Line Items]
Long-term debt, gross										$ 7,500,000
Deb maturity date										Jan. 1, 2020

Convertible Notes - Additional

Convertible Notes - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended
	Jun. 30, 2018	Apr. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Debt Instrument [Line Items]
Convertible notes issued to existing shareholders of redeemable convertible and convertible preferred stock		$ 14,400,000
Minimum threshold percentage on convertible notes to extend maturity date		80.00%
Conversion price per share	$ 4.7565
Convertible notes qualified financing		$ 25,000,000
Convertible notes non-qualified financing		$ 25,000,000
Principal and accrued interest on convertible notes	$ 14,600,000
Loss on extinguishment of convertible notes	$ 400,000					$ 370,000
Interest expense			$ 100,000	$ 200,000	$ 600,000	500,000
Series F Preferred Stock
Debt Instrument [Line Items]
Conversion price per share		$ 3.8590
Series G Redeemable Convertible Preferred Stock
Debt Instrument [Line Items]
Issuance of redeemable convertible preferred stock	1,067,550
Convertible Preferred Stock
Debt Instrument [Line Items]
Issuance of redeemable convertible preferred stock	1,997,709
Convertible Notes
Debt Instrument [Line Items]
Convertible notes annual interest rate		8.00%
Preferred stock issuance price percentage		90.00%
Liability recognized on estimated fair value of embedded derivative		$ 400,000
Debt issuance costs		$ 100,000
Interest expense						200,000
Convertible Notes | Other Expense, Net
Debt Instrument [Line Items]
Change in fair value of convertible notes embedded derivative liability						$ 1,200,000

Convertible Preferred Stock a_3

Convertible Preferred Stock and Redeemable Convertible Preferred Stock - Additional Information (Details)	Jul. 02, 2019shares
Initial Public Offering
Temporary Equity [Line Items]
Convertible preferred stock converted into common stock	58,363,606

Convertible Preferred Stock a_4

Convertible Preferred Stock and Redeemable Convertible Preferred Stock - Summary of Convertible Preferred Stock and Redeemable Convertible Preferred Stock (Details) $ in Thousands	Dec. 31, 2018USD ($)shares
Temporary Equity [Line Items]
Shares Authorized	105,003,754
Shares Issued	104,778,246
Shares Outstanding	104,778,246
Net Carrying Value | $	$ 294,200
Aggregate Liquidation Preference | $	$ 301,346
Series A
Temporary Equity [Line Items]
Shares Authorized	18,960,000
Shares Issued	18,941,619
Shares Outstanding	18,941,619
Net Carrying Value | $	$ 9,161
Aggregate Liquidation Preference | $	$ 9,217
Series B
Temporary Equity [Line Items]
Shares Authorized	13,784,443
Shares Issued	13,652,791
Shares Outstanding	13,652,791
Net Carrying Value | $	$ 13,774
Aggregate Liquidation Preference | $	$ 14,000
Series C
Temporary Equity [Line Items]
Shares Authorized	9,335,659
Shares Issued	9,328,791
Shares Outstanding	9,328,791
Net Carrying Value | $	$ 20,289
Aggregate Liquidation Preference | $	$ 20,374
Series D
Temporary Equity [Line Items]
Shares Authorized	14,367,652
Shares Issued	14,324,642
Shares Outstanding	14,324,642
Net Carrying Value | $	$ 39,886
Aggregate Liquidation Preference | $	$ 40,000
Series E
Temporary Equity [Line Items]
Shares Authorized	13,612,543
Shares Issued	13,586,946
Shares Outstanding	13,586,946
Net Carrying Value | $	$ 39,880
Aggregate Liquidation Preference | $	$ 40,000
Series F Preferred Stock
Temporary Equity [Line Items]
Shares Authorized	12,956,724
Shares Issued	12,956,724
Shares Outstanding	12,956,724
Net Carrying Value | $	$ 54,968
Aggregate Liquidation Preference | $	$ 57,211
Series G
Temporary Equity [Line Items]
Shares Authorized	21,986,733
Shares Issued	21,986,733
Shares Outstanding	21,986,733
Net Carrying Value | $	$ 116,242
Aggregate Liquidation Preference | $	$ 120,544

Share-based Compensation Plan_2

Share-based Compensation Plans - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended			9 Months Ended		12 Months Ended
	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2011
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation expense			$ 2,520		$ 740	$ 4,916	$ 1,966
Selling, General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation expense			$ 1,277	$ 800	$ 459	$ 2,565	$ 1,076	$ 800
Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares issued in transaction	382,477	432,270
Sale of stock, price per share	$ 12.72	$ 9.0902		$ 12.72	$ 9.0902		$ 9.0902
Sale of stock, aggregate amount	$ 4,900	$ 3,900
Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized			1,750,000			1,750,000
Employee Stock Purchase Plan | First Business Day
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted as percentage on fair value of stock						85.00%
Employee Stock Purchase Plan | Last Business Day
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted as percentage on fair value of stock						85.00%
2011 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period									4 years
Percentage of maximum incentive stock options granted to stockholders									10.00%
2011 Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options exercisable period									10 years
2011 Plan | Incentive and Non-statutory Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized									12,987,255
2011 Plan | Incentive and Non-statutory Stock Options | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted as percentage on fair value of stock									100.00%
2011 Plan | Incentive Stock Options | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted as percentage on fair value of stock									110.00%
2019 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized			8,000,000			8,000,000

Share-based Compensation Plan_3

Share-based Compensation Plans - Schedule of Total Stock-based Compensation Expense, Excluding Compensation Expense Related to Stock Sales, by Function (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 2,520		$ 740	$ 4,916	$ 1,966
Marketing
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	145		42	287	115
Operations and Technology
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	1,098		239	2,064	775
Selling, General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 1,277	$ 800	$ 459	$ 2,565	$ 1,076	$ 800

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2018USD ($)Installment	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)
Other Commitments [Line Items]
Operating lease rent expense		$ 4.8	$ 2.7	$ 13.4	$ 6.9
Outstanding liability		0.9		0.9
Selling, General and Administrative
Other Commitments [Line Items]
Estimated fair value of grant expense	$ 1.7
Fair value of grant, discount rate	10.00%
Endowment Agreement
Other Commitments [Line Items]
Donation fund	$ 2
Annual installment payment of donation fund	$ 0.5
Number of annual installments | Installment	4
Other Accrued and Current Liabilities
Other Commitments [Line Items]
Deferred rent, current		0.8		0.8
Outstanding liability		0.4		0.4
Other Noncurrent Liabilities
Other Commitments [Line Items]
Deferred rent, noncurrent		6.8		6.8
Outstanding liability		$ 0.5		$ 0.5
Minimum [Member]
Other Commitments [Line Items]
Operating lease term		1 year		1 year
Maximum
Other Commitments [Line Items]
Operating lease term		11 years		11 years

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Future Minimum Lease Payments Under Noncancelable Operating Leases (Details) $ in Thousands	Sep. 30, 2019USD ($)
Commitments And Contingencies Disclosure [Abstract]
2019	$ 4,728
2020	19,439
2021	19,455
2022	16,733
2023	15,539
Thereafter	64,537
Total future minimum payments	$ 140,431

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Reconciliation of Numerator and Denominator Used in Calculation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator
Net loss attributable to common stockholders	$ (25,274)	$ (25,085)	$ (78,726)	$ (59,237)
Denominator
Weighted-average common shares outstanding used to calculate net loss per share attributable to common stockholders, basic and diluted	84,634,956	8,349,403	34,556,485	8,321,296
Net loss per share attributable to common stockholders, basic and diluted	$ (0.30)	$ (3)	$ (2.28)	$ (7.12)

Net Loss Per Share - Schedule_2

Net Loss Per Share - Schedule of Anti-dilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Details) - shares	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	9,969,039	62,072,753
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share		36,862,298
Redeemable Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share		16,410,256
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	9,417,490	8,628,662
Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	551,549
Warrants | Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share		103,563
Warrants | Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share		67,974