(7) Stock‑Based Compensation

The Company has two equity incentive plans: the 2012 Stock Incentive Plan and the Amended and Restated 2019 Equity Incentive Plan. New awards can only be granted under the Amended and Restated 2019 Equity Incentive Plan (the “Plan”). At March 31, 2021, 873,688 shares were available for future issuances under the Plan. The Plan is subject to an annual increase, subject to prior approval by the Company’s board of directors, equal to the lesser of (i) 432,442 shares, (ii) 4% of the shares outstanding on the last day of the immediately preceding fiscal year and (iii) such smaller number of shares as determined by the board of directors. The Plan provides for the grant of incentive stock options, nonqualified stock options, restricted stock awards, restricted stock units and/or stock appreciation rights to employees, directors, and other persons, as determined by the Company’s board of directors. The Company estimates forfeitures that it expects will occur and adjusts expense for actual forfeitures in the periods they occur.

The Company measures employee and nonemployee stock‑based awards at grant‑date fair value and records compensation expense ratably over the vesting period of the award. The Company recorded stock‑based compensation expense in the following expense categories of its accompanying consolidated statements of operations and comprehensive loss (in thousands):


	Three months ended March 31,
	2021		2020
Sales and marketing	$	184	$	161
General and administrative		366		209
Research and development		144		79
Total stock‑based compensation	$	694	$	449

Stock Options

The Company’s stock options vest based on the terms in each award agreement and generally vest over four years and have a term of 10 years. The following table summarizes stock option activity for the Plan:


				Weighted
				average
		Weighted		remaining
	Number of	average exercise		contractual term
	shares	price per share		(years)
Outstanding at January 1, 2021	1,498,208		10.87
Granted	180,575		16.99
Exercised	(3,122)		11.46
Canceled/forfeited	(41,339)		12.72
Outstanding at March 31, 2021	1,634,322	$	11.50	7.80
Vested and expected to vest at March 31, 2021	1,570,634	$	11.41	7.76
Exercisable at March 31, 2021	729,909	$	8.86	6.50

At March 31, 2021, the aggregate intrinsic value of outstanding options and exercisable options was $6.1 million and $4.4 million, respectively.

The 2012 Stock Incentive Plan provided the holders of stock options an election to early exercise prior to vesting. The Company has the right, but not the obligation, to repurchase early exercised options without transferring any appreciation to the employee if the employee terminates employment before the end of the original vesting period. The repurchase price is the lesser of the original exercise price or the then fair value of the common stock. At March 31, 2021, $1,000 of proceeds from early exercised options are recognized as a current liability in other current liabilities in the accompanying consolidated balance sheet.

The following table summarizes activity relating to early exercise of stock options:


		Number of
		shares
Unvested balance at January 1, 2021		182
Vested		(46)
Unvested balance at March 31, 2021		136

The weighted average grant‑date fair value per share of options granted was $10.01 during the three months ended March 31, 2021. The aggregate intrinsic value of options exercised was $12,000 for the three ended March 31, 2021. At March 31, 2021, the total unrecognized compensation expense related to unvested employee and nonemployee stock option awards was $5.8 million, which is expected to be recognized in expense over a weighted‑average period of approximately 2.6 years.

Estimating Fair Value of Stock Options

The fair value of each grant of stock options was determined by the Company using the methods and assumptions discussed below. Certain of these inputs are subjective and generally requires judgment to determine.

Expected term – The expected term of stock options represents the weighted average period the stock options are expected to be outstanding. The Company uses the simplified method for estimating the expected term as provided by the Securities and Exchange Commission. The simplified method calculates the expected term as the average time to vesting and the contractual life of the options.

Expected volatility – Due to the Company’s limited operating history and lack of adequate company‑specific historical or implied volatility, the expected volatility assumption was determined by examining the historical volatilities of a group of industry peers whose share prices are publicly available.

Risk‑free interest rate – The risk‑free rate assumption is based on the U.S. Treasury instruments, the terms of which were consistent with the expected term of the Company’s stock options.

Expected dividend – The Company has not paid and does not intend to pay dividends.

The fair value of each option was estimated on the date of grant using the weighted average assumptions in the table below:


	Three months ended
	March 31, 2021
Expected dividend yield	—
Expected volatility	64.3	%
Risk‑free interest rate	0.82	%
Expected term (in years)	6.25

Restricted Stock Units

The Company’s restricted stock units vest based on the terms in each award agreement and generally vest over four years. The following table summarizes restricted stock units for the Plan:


		Number of
		shares
Outstanding at January 1, 2021		—
Granted		186,732
Canceled/forfeited		(855)
Outstanding at March 31, 2021		185,877

The weighted average grant‑date fair value per restricted stock unit granted was $16.63 during the three months ended March 31, 2021. The aggregate intrinsic value of restricted stock units was $2.8 million at March 31, 2021. The total unrecognized compensation expense at March 31, 2021 related to restricted stock units was $2.2 million, which is expected to be recognized in expense over a weighted‑average period of approximately 3.9 years.