Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement [Abstract]

Schedule of Stock-based Compensation Expense

Stock-based compensation expense included in the consolidated statements of operations was as follows (in thousands):

	Year Ended December 31,
	2021		2020		2019
Infrastructure and trust & safety	$	35,255	$	7,396	$	2,085
Research and development	219,851		39,402		9,695
General and administrative	72,929		25,939		3,347
Sales and marketing	13,907		6,421		2,507
Total stock-based compensation	$	341,942	$	79,158	$	17,634

Schedule of Valuation Assumptions

The assumptions used in the Black-Scholes pricing model for stock-based compensation for the periods below were as follows:

	Year Ended December 31,
	2020	2019
Risk-free interest rate	0.5% -1.8%	1.5% -1.7%
Expected volatility	35.4% - 39.8%	37.0% - 40.8%
Dividend yield	—	—
Expected terms (in years)	7	6 - 7
Fair value of common stock	$4.61 - $21.06	$3.35 - $4.01

	Year Ended
	December 31, 2021
Risk-free interest rate	0.06%	-	0.25%
Expected volatility	46.97%	-	56.91%
Dividend yield	—%
Expected terms (in years)	0.44	-	2.00

Schedule of Summarizes the Company's Stock Option Activity

The following table summarizes stock option activity under the Plan (in thousands except per share data and remaining contractual term):

	Options Outstanding
	Number of Shares Subject to Options	Weighted- Average Exercise Price		Remaining Contractual Term (Years)	Aggregate Intrinsic Value
Balances as of December 31, 2018	83,395	$	0.90
Granted	31,381	$	3.38
Cancelled	(6,199)	$	2.10
Exercised	(8,895)	$	0.36
Balances as of December 31, 2019	99,682	$	1.66	7.84	$	174,497
Granted	23,269	$	4.73
Cancelled	(3,859)	$	2.39
Exercised	(20,590)	$	0.74
Balances as of December 31, 2020	98,502	$	2.55	7.76	$	3,838,994
Granted	—	—
Cancelled	(1,862)	$	3.95
Exercised	(33,373)	$	1.95
Balances as of December 31, 2021	63,267	$	2.82	6.97	$	6,348,395
Exercisable as of December 31, 2021	35,431	$	1.86	6.19	$	3,589,069
Vested and expected to vest at December 31, 2021	63,267	$	2.82	6.97	$	6,348,395

Schedule of Company's Restricted Stock Units and Unregistered Restricted Stock Awards Activity

The following table summarizes RSUs and unregistered restricted stock awards (“unregistered RSAs”) activity (in thousands except per share data):

	Restricted Stock Units			Restricted Stock Awards
	Number of Shares	Weighted- Average grant date value		Number of Shares	Weighted- Average grant date fair value
Unvested as of December 31, 2019	30	$	3.35	—	—
Granted	3,061	$	31.55	388	$	37.75
Vested	(30)	$	3.35	—	—
Unvested as of December 31, 2020	3,061	$	31.55	388	$	37.75
Granted	13,382	$	78.92	209	$	81.67
Vested	(1,376)	$	38.46	(129)	$	37.75
Cancelled	(383)	$	52.78	—	—
Unvested as of December 31, 2021	14,684	$	68.03	468	$	57.37

Disclosure of Founder CEO Long Term Performance Award

The CEO Long-Term Performance Award is divided into seven tranches that are eligible to vest based on the achievement of stock price goals, each a Company Stock Price Hurdle, measured based on an average of our stock price over a consecutive 90-day trading period applicable to the performance period as set forth below.

	Company Stock Price Hurdle		Number of RSUs Eligible to Vest	Performance Period Commencement Dates as Measured from the Effective Date
1	$	165.00	750,000	2 years
2	$	200.00	750,000	3 years
3	$	235.00	2,000,000	4 years
4	$	270.00	2,000,000	5 years
5	$	305.00	2,000,000	5 years
6	$	340.00	2,000,000	5 years
7	$	375.00	2,000,000	5 years