STOCK-BASED COMPENSATION (Tables)

6 Months Ended

Jun. 30, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

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):

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Cost of revenue	$	397	$	270	$	632	$	508
Research and development		675		636		1,311		1,156
Selling and marketing		454		343		748		559
General and administrative		4,929		4,554		12,258		9,081
Total stock-based compensation expense	$	6,455	$	5,803	$	14,949	$	11,304

Summary of Incentive Stock Units

The table below summarizes the Company’s activity and related information for its ISUs:

	ISUs
	Number of Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2020		8,046,399		$	3.41
ISUs granted		3,178,689		$	4.78
ISUs vested		(3,509,497	)	$	4.82
ISUs forfeited		(178,503	)	$	3.34
Unvested at June 30, 2021		7,537,088		$	3.99
Vested and unreleased		172,692
Outstanding at June 30, 2021		7,709,780

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, 2020		8,142,348		$	7.14		7.3	$	2,638
Options granted		—			—
Options exercised		(43,651	)	$	4.26
Options cancelled or forfeited		(680,493	)	$	9.20
Options outstanding at June 30, 2021		7,418,204		$	6.97		6.7	$	7,905
Options exercisable at June 30, 2021		5,452,385		$	6.94		6.3	$	5,559
Options vested and expected to vest at June 30, 2021		7,260,596		$	7.00		6.6	$	7,573

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:

	Six Months Ended June 30,
	2020
Expected term (in years)		6.0
Expected volatility	68.8%
Risk-free interest rate	0.7%
Expected dividend yield	0.0%