Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2022

Share-Based Payment Arrangement [Abstract]

Summary of Stock Options Activity

A summary of stock option activity for the six months ended June 30, 2022 is as follows:

	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)
Outstanding at January 1, 2022		5,919		$	8.82		4.36	$	4,205
Granted		1,516			3.89
Exercised		(130	)		1.95
Forfeited		(195	)		7.98
Outstanding at June 30, 2022		7,110		$	7.92		4.80	$	851
Options exercisable at June 30, 2022		5,474		$	9.04		3.35	$	544
Vested or expected to vest at June 30, 2022		7,001		$	7.98		4.70	$	834

Assumptions of Estimated Fair Value of Option on the Date of Grant Using Black-Scholes Option Pricing Model

The fair value of each option is estimated on the date of grant using the Black-Scholes option-pricing model using the following assumptions:

	Three Months Ended June 30,		Six Months Ended June 30,
	2022	2021	2022	2021
Risk-free interest rate	3.0%–3.2%	1.0%	1.7%–3.2%	1.0%
Expected term (in years)	5.6–6.3	6.1	5.6–6.3	6.1
Expected volatility	40.5%–41.5%	38.2%	38.5%–41.5%	38.2%
Expected dividend yield	0.0%	0.0%	0.0%	0.0%

Summary of RSU Activity

A summary of RSU activity for the six months ended June 30, 2022 is as follows:

	Number of Shares			Weighted- Average Grant Date Fair Value		Aggregate Fair Value
Unvested balance at January 1, 2022		4,309		$	6.34
Granted		2,252			3.66
Vested		(1,097	)		6.65	$	4,989
Forfeited		(356	)		6.35
Unvested balance at June 30, 2022		5,108		$	5.09

Summary of PSU Activity

A summary of PSU activity for the six months ended June 30, 2022 is as follows:

	Number of Shares			Weighted- Average Grant Date Fair Value		Aggregate Fair Value
Unvested balance at January 1, 2022		442		$	7.89
Granted		846			2.79
Vested		—			—	$	—
Forfeited		(26	)		7.89
Unvested balance at June 30, 2022		1,262		$	4.47

Assumptions of Estimated Based on Monte Carlo Simulation Model

Compensation expense is based on the estimated value of the awards on the grant date, and is recognized over the period from the grant date through the expected vest dates of each vesting condition, both of which were estimated based on a Monte Carlo simulation model applying the following key assumptions:

	Three months ended June 30,		Six months ended June 30,
	2022	2021	2022	2021
Risk-free interest rate	2.8%	*	2.8%	0.2%
Volatility	79.1%	*	79.1%	78.6%
Dividend yield	0.0%	*	0.0%	0.0%
Cost of equity	13.2%	*	13.2%	12.0%

* No PSUs were granted during the three months ended June 30, 2021.

Summary of SAR Activity

A summary of SAR activity for the six months ended June 30, 2022 is as follows:

	Number of Shares			Weighted- Average Exercise Price
Outstanding at January 1, 2022		200		$	7.28
Granted		—			—
Exercised		(90	)		1.69
Forfeited		—			—
Outstanding at June 30, 2022		110		$	11.86

Schedule of Stock-based Compensation Expense

Stock-based compensation expense related to stock options, RSUs, SARs and PSUs for the three and six months ended June 30, 2022 and 2021 was classified in the condensed consolidated statements of operations and comprehensive (loss) income as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Cost of revenue	$	26	$	33	$	61	$	66
Research and development expenses		694		543		1,289		1,414
Selling, general and administrative expenses		2,159		3,518		4,157		6,067
Total stock-based compensation	$	2,879	$	4,094	$	5,507	$	7,547

The Company recognized stock-based compensation expense for the three and six months ended June 30, 2022 and 2021 in the condensed consolidated balance sheet as follows:

	Three Months Ended June 30,						Six Months Ended June 30,
	2022			2021			2022			2021
Change in fair value of SAR Liability	$	(56	)	$	(59	)	$	(159	)	$	289
Recognized as additional paid-in capital		2,935			4,153			5,666			7,258
Total stock-based compensation	$	2,879		$	4,094		$	5,507		$	7,547