Equity Incentive Plans (Tables)

3 Months Ended

Mar. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Changes in Shares Available for Grant

Changes in shares available for grant during the three months ended March 31, 2021 were as follows:

	Shares Available for Grant
Shares available for grant at December 31, 2020		18,617,001
2019 Plan reserve increase on January 1, 2021		6,882,344
Options and restricted stock units granted		(2,240,923	)
Options and restricted stock units forfeited, cancelled or expired		342,310
Shares available for grant at March 31, 2021		23,600,732

Summary of Stock Option Activity Under 2009 Plan and 2019 Plan

Stock option activity under the 2009 Plan and 2019 Plan during the three months ended March 31, 2021 was as follows:

	Shares Subject to Outstanding Options			Weighted-Average Exercise Price per Share		Aggregate Intrinsic Value (in thousands)
Options outstanding at December 31, 2020		14,433,560		$	12.82	$	668,458
Options granted		1,635,608			45.33
Options forfeited or cancelled		(328,594	)		15.47
Options expired		(10,050	)		0.19
Options exercised		(2,183,640	)		6.61
Options outstanding at March 31, 2021		13,546,884		$	17.69	$	319,063
Options vested and exercisable at March 31, 2021		6,853,224		$	8.56	$	217,592

Summary of Restricted Stock Unit Activity

Restricted stock unit activity under the 2019 Plan during the three months ended March 31, 2021 was as follows:

	Restricted Stock Units Outstanding			Weighted-Average Grant Date Fair Value per Share
Nonvested outstanding restricted stock units at December 31, 2020		50,000		$	28.10
Restricted stock units granted		605,315			44.10
Restricted stock units forfeited or cancelled		(3,666	)		62.40
Nonvested outstanding restricted stock units at March 31, 2021		651,649		$	42.77

Summary of Estimated Grant Date Fair Value of Options Granted

The estimated grant date fair value of options granted during the three months ended March 31, 2021 and 2020 was estimated using the Black-Scholes option-pricing model with the following assumptions:

	Three Months Ended March 31,
	2021		2020
Fair value of common stock	$43.68 - $66.50		$17.68 - $31.71
Expected term (in years)	5.27 - 6.08		5.27 - 6.08
Risk-free interest rate	0.5% - 1.1%		0.7% - 1.7%
Expected volatility	67.1% - 68.4%		70.5% - 72.1%
Expected dividend yield		—		—

Summary of Compensation Costs Related to Stock Options and RSUs Included on Statements of Operations

The compensation costs related to stock options and restricted stock units for the three months ended March 31, 2021 and 2020 are included on our statements of operations as follows (in thousands):

	Three Months Ended March 31,
	2021		2020
Cost of revenue	$	328	$	172
Research and development		2,883		1,544
Sales and marketing		2,495		1,157
General and administrative		2,778		1,802
Total share-based compensation expense	$	8,484	$	4,675