Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Summary of Stock-Based Compensation Expense

Total stock-based compensation expense recognized in the Company’s consolidated statements of operations and comprehensive loss is classified as follows (in thousands):

	Year Ended December 31,
	2020		2019		2018
Cost of revenue	$	965	$	2,645	$	1,609
Research and development		2,288		3,910		2,681
Selling and marketing		1,091		1,365		736
General and administrative		18,461		11,525		9,143
Total stock-based compensation expense	$	22,805	$	19,445	$	14,169

Summary of RSU Activity

A summary of the Company’s RSU activity and related information is as follows:

	Number of Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2019		4,379,777		$	5.14
RSUs granted		6,079,659		$	2.80
RSUs vested		(1,779,152	)	$	5.69
RSUs cancelled or forfeited		(633,885	)	$	3.11
Unvested at December 31, 2020		8,046,399		$	3.41
Vested and unreleased		177,007
Outstanding at December 31, 2020		8,223,406

Summary of Company's Stock Option Activity and Related Information

A summary of the Company’s stock option activity and related information is as follows:

	Number of Stock Options Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value
								(In thousands)
Options outstanding at December 31, 2019		11,165,846		$	7.44		7.6	$	1,907
Options granted		736,579			1.97
Options exercised		(20,579	)		0.72
Options cancelled or forfeited		(3,739,498	)		6.95
Options outstanding at December 31, 2020		8,142,348		$	7.14		7.3	$	2,638
Options exercisable at December 31, 2020		5,319,817		$	7.20		6.8	$	1,354
Options vested and expected to vest at December 31, 2020		7,875,294		$	7.18		7.2	$	2,438

Schedule of Weighted-Average Assumptions Used in Black-Scholes Option-Pricing Model to Estimate Fair Value of Employee Stock Options at Grant Date

The fair value of employee stock options was estimated at the date of grant using a Black-Scholes option-pricing model with the following weighted-average assumptions:

	Year Ended December 31,
	2020		2019		2018
Expected term (in years)		6.0		6.0		6.0
Expected volatility (%)	68.8%		60.7%		60.4%
Risk-free interest rate (%)	0.7%		2.4%		2.8%
Expected dividend yield (%)	0%		0%		0%

2015 Employee Stock Purchase Plan

Schedule of Weighted-Average Assumptions Used in Black-Scholes Option-Pricing Model to Estimate Fair Value of Employee Stock Purchases at Grant Date

The fair value of each purchase right granted under the ESPP was estimated on the date of grant using the Black-Scholes option-pricing model with the following assumptions:

	Year Ended December 31,
	2020	2019	2018
Expected term (in years)	0.25 - 0.50	N/A	N/A
Expected volatility (%)	83.0%	N/A	N/A
Risk-free interest rate (%)	0.09% - 0.17%	N/A	N/A
Expected dividend yield (%)	0%	N/A	N/A