CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net loss	$ (51,550)	$ (30,935)	$ (32,450)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	16,553	13,400	9,642
Amortization of deferred rent	(711)	(340)	265
Amortization of debt issuance costs	1,909	0	161
Stock-based compensation	12,145	4,079	2,809
Provision for doubtful accounts	360	599	1,024
Change in fair value of preferred stock warrant liabilities	2,404	606	176
Other adjustments	(591)	(354)	(18)
Interest paid on capital leases	(364)	(203)	(105)
Loss on disposals of property and equipment	108	0	113
Changes in operating assets and liabilities:
Accounts receivable	(12,767)	(6,234)	(6,043)
Prepaid expenses and other current assets	(2,095)	(2,325)	(3,537)
Other assets	(2,222)	10	(94)
Accounts payable	2,391	(372)	1,109
Accrued expenses	4,401	3,902	1,009
Other liabilities	(1,274)	1,182	78
Net cash used in operating activities	(31,303)	(16,985)	(25,861)
Cash flows from investing activities:
Purchases of marketable securities	(190,980)	(62,660)	(46,071)
Sales of marketable securities	52,589	0	0
Maturities of marketable securities	70,813	35,210	43,539
Purchases of property and equipment	(14,609)	(16,702)	(12,099)
Capitalized internal-use software	(4,856)	(2,955)	(1,149)
Purchases of intangible assets	(635)	0	0
Net cash used in investing activities	(87,678)	(47,107)	(15,780)
Cash flows from financing activities:
Proceeds from initial public offering, net of underwriting discounts	192,510	0	0
Proceeds from borrowings under notes payable	20,300	29,411	12,774
Payments of debt issuance costs	(231)	(257)
Repayments of notes payable	(49,167)	(833)	(7,383)
Repayments of capital leases	(1,370)	(1,215)	(464)
Proceeds from Employee Stock Purchase Plan	5,402	0	0
Proceeds from exercise of vested stock options	5,579	1,561	611
Proceeds from early exercise of stock options	520	1,054	5
Proceeds from payment of stockholder note	74	50	0
Repurchase of early exercised shares	0	(13)	0
Net cash provided by financing activities	168,148	69,637	55,406
Effects of exchange rate changes on cash, cash equivalents, and restricted cash	99	22	(32)
Net increase in cash, cash equivalents, and restricted cash	49,266	5,567	13,733
Cash, cash equivalents, and restricted cash at beginning of period	36,963	31,396	17,663
Cash, cash equivalents, and restricted cash at end of period	86,229	36,963	31,396
Supplemental disclosure of cash flow information:
Cash paid for interest	5,422	1,833	996
Cash paid for income taxes, net of refunds received	361	55	166
Property and equipment additions not yet paid in cash	7,071	133	1,838
Vesting of early-exercised stock options	620	337	248
Capital lease outstanding from current year addition	7,380	429	4,324
Warrant issued in connection with debt	0	1,639	0
Conversion of convertible preferred stock warrants to convertible common stock warrants	5,665	0	0
Cashless exercise of common stock warrants	1,036	0	0
Costs related to initial public offering, accrued but not yet paid	130	0	0
Stock-based compensation capitalized to internal-use software	441	0	0
Reconciliation of cash, cash equivalents, and restricted cash as shown in the statements of cash flows
Total cash, cash equivalents, and restricted cash	36,963	31,396	31,396
IPO
Cash flows from financing activities:
Payments of issuance costs	(5,469)	0	0
Series E Preferred Stock
Cash flows from financing activities:
Proceeds from financing	0	0	50,000
Series E Preferred Stock | Convertible preferred stock
Cash flows from financing activities:
Payments of issuance costs	0	0	(137)
Series F Preferred Stock
Cash flows from financing activities:
Proceeds from financing	0	40,000	0
Series F Preferred Stock | Convertible preferred stock
Cash flows from financing activities:
Payments of issuance costs	$ 0	$ (121)	$ 0