Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Net revenue	$ 517,175	$ 290,292	$ 143,267
Costs of revenue	285,470	172,385	82,814
Gross profit	231,705	117,907	60,453
Operating expenses:
Compensation and benefits	318,116	129,802	88,309
Professional services	18,443	7,188	7,157
Technology	33,637	13,239	7,796
Occupancy	4,181	4,337	3,777
Depreciation and amortization	3,534	3,498	3,080
Marketing and advertising	2,284	1,670	2,080
Other operating expenses	13,516	5,260	7,117
Total operating expenses	393,711	164,994	119,316
Loss from operations	(162,006)	(47,087)	(58,863)
Other income (expense), net	(2,563)	(521)	698
Loss before income tax expense	(164,569)	(47,608)	(58,165)
Income tax expense (benefit)	(640)	87	35
Net loss	(163,929)	(47,695)	(58,200)
Deemed dividend to redeemable convertible preferred stockholders	0	0	(64,149)
Net loss attributable to Class A and Class B common stockholders	(163,929)	(47,695)	(122,349)
Other comprehensive income (loss), net of taxes:
Change in foreign currency translation adjustment	(14)	(64)	(22)
Change in unrealized gain (loss) on marketable securities	(2,241)	43	69
Net other comprehensive income (loss)	(2,255)	(21)	47
Comprehensive loss	$ (166,184)	$ (47,716)	$ (58,153)
Net loss per share attributable to common stockholders, basic (in dollars per share)	$ (0.45)	$ (0.39)	$ (1.07)
Net loss per share attributable to common stockholders, diluted (in dollars per share)	$ (0.45)	$ (0.39)	$ (1.07)
Weighted-average shares used in computing net loss per share attributable to common stockholders - Basic (in shares)	362,756,466	122,932,556	113,851,714
Weighted-average shares used in computing net loss per share attributable to common stockholders - Diluted (in shares)	362,756,466	122,932,556	113,851,714