Stock Based Compensation (Tables)

9 Months Ended

Sep. 30, 2021

Share-based Payment Arrangement [Abstract]

Summary of Stock-Based Compensation Expense

The following table summarizes stock-based compensation expense recognized for the three and nine months ended September 30, 2021 and 2020 as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2021		2020		2021		2020
Research and development	$	1,814	$	523	$	5,237	$	1,544
Sales and marketing	1,637		468		6,025		1,542
General and administrative	12,361		2,671		31,269		6,479
Total stock-based compensation expense	$	15,812	$	3,662	$	42,531	$	9,565

Summary of Stock Option and RSU Activity

Stock option and RSU activity during the nine months ended September 30, 2021 is as follows (in thousands, except for share, per share, and contractual term data):

		Options Outstanding						Restricted Stock Units
	Number of Shares Available for Issuance Under the Plan	Number of Shares Outstanding Under the Plan	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value		Number of Plan shares outstanding	Weighted-Average Grant Date Fair Value per share
Balance at December 31, 2020	35,500,603	38,404,493	$	5.89	8.27	$	542,074	341,256	$	17.68
Options and restricted stock units granted	(3,743,376)	64,839	12.58					3,678,537	20.28
Options exercised and restricted stock units released	—	(4,896,629)	0.65					(20,303)	17.48
Options and restricted stock units canceled	4,039,561	(3,390,960)	1.22					(648,601)	22.46
Balance at September 30, 2021	35,796,788	30,181,743	$	7.24	7.31	$	172,203	3,350,889	$	19.61
Exercisable at December 31, 2020		14,248,234	$	0.18	6.45	$	282,364
Exercisable at September 30, 2021		13,459,112	0.16		5.37	129,935
Unvested at December 31, 2020		24,156,259	9.25		9.34	259,710
Unvested at September 30, 2021		16,722,631	12.93		8.87	42,268

Summary of Stock Option Valuation Assumptions

The assumptions used to estimate the fair value of stock options granted and the resulting fair values for the three and nine months ended September 30, 2021 and 2020 were as follows:

	Three Months Ended September 30,		Nine Months Ended September 30,
	2021(1)	2020	2021(1)	2020
Expected volatility	48.71%	48.65% - 48.9%	48.71%	47.24% - 48.93%
Risk-free interest rate	0.02%	0.35% - 0.41%	0.02%	0.35% - 1.44%
Expected term (in years)	0.25	6.00 - 6.1	0.25	6.00 - 6.25
Expected dividend yield	—	—	—	—
Weighted average estimated fair value of stock options granted during the period	$15.63	$7.95	$15.63	$2.98

(1)For the three and nine months ended September 30, 2021, the above assumptions were used to estimate the fair value of certain stock options previously granted to the CFO, that were modified as part of the transition and release agreement.