Equity Incentive Plans (Tables)

12 Months Ended

Dec. 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 year ended December 31, 2021 were as follows:

	Shares Available for Grant
Shares available for grant at December 31, 2020		18,617,001
2019 Equity Incentive Plan reserve increase effective January 1, 2021		6,882,344
Options and restricted stock units granted		(4,306,265	)
Options and restricted stock units forfeited, cancelled or expired		1,106,843
Shares available for grant at December 31, 2021		22,299,923

Summary of Stock Option Activity Under 2008 Plan 2009 Plan and 2019 Plan

Stock option activity under the 2009 Plan and 2019 Plan during the year ended December 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
Options granted		3,052,025			39.39
Options forfeited or cancelled		(992,428	)		25.90
Options expired		(40,116	)		26.56
Options exercised		(3,674,057	)		7.21
Options outstanding at December 31, 2021		12,778,984		$	19.72	$	156,105
Options vested and exercisable at December 31, 2021	7,281,600			$	10.99	$	132,537

Summary of Restricted Stock Unit Activity

Restricted stock unit activity under the 2019 Plan during the year ended December 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		1,254,240			37.98
Restricted stock units forfeited or cancelled		(74,299	)		43.20
Restricted stock units vested		(18,750	)		28.10
Nonvested outstanding restricted stock units at December 31, 2021		1,211,191		$	37.41

Summary of Estimated Grant Date Fair Values of Options Granted

The estimated grant date fair values of options granted during the years ended December 31, 2021, 2020 and 2019 were estimated using the Black-Scholes option-pricing model with the following assumptions:

	Year Ended December 31,
	2021		2020		2019
Fair value of common stock	$30.86 - $66.50		$17.68 - $55.23		$7.80 - $47.81
Expected term (in years)	5.27 - 6.08		5.27 - 6.08		5.27 - 6.08
Risk-free interest rate	0.5% - 1.4%		0.4% - 1.7%		1.4% - 2.5%
Expected volatility	67.1% - 70.0%		70.5% - 73.3%		64.3% - 72.9%
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 years ended December 31, 2021, 2020 and 2019 are included on our consolidated statements of operations as follows (in thousands):

	Year Ended December 31,
	2021		2020		2019
Cost of revenue	$	2,100	$	817	$	555
Research and development		14,061		8,519		3,934
Sales and marketing		12,312		6,627		3,480
General and administrative		14,778		8,798		5,155
Total share-based compensation expense	$	43,251	$	24,761	$	13,124