In April 2021, the Company’s board of directors adopted, and in May 2021 its stockholders approved the 2021 Equity Incentive Plan (the 2021 Plan).

No further awards are being made under the Company’s 2009 Equity Incentive Plan, as amended (the 2009 Plan) or the Company’s 2018 Stock Incentive Plan (the 2018 Plan); however, awards outstanding under each of the 2009 Plan and 2018 Plan will continue to be governed by their existing terms. With the establishment of the 2021 Plan as further discussed below, upon the expiration, forfeiture, cancellation, or reacquisition of any stock-based awards granted under the 2009 Plan or 2018 Plan, an equal number of shares will become available for grant under the 2021 Plan. The 2021 Plan, 2018 Plan and 2009 Plan are collectively referred to as the “Equity Incentive Plans”.

The 2021 Plan provides for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock awards, restricted stock units, performance awards and other forms of equity compensation (collectively, equity awards). A total of 19,988,330 shares of the Company’s common stock have been reserved for issuance under the 2021 Plan in addition to (i) any annual automatic evergreen increases in the number of shares of common stock reserved for issuance under the 2021 Plan and (ii) upon the expiration, forfeiture, cancellation, or reacquisition of any stock-based awards granted under the 2009 Plan or 2018 Plan, an equal number of shares of common stock will become available under the 2021 Plan.

As of March 31, 2023, a total of 14,955,684 shares of the Company's common stock were available for future issuance under the 2021 Plan.

Stock options granted under the 2009 Plan, 2018 Plan and the 2021 Plan generally vest based on continued service over four years and expire within ten years from the date of grant. Any options that are canceled or forfeited before expiration become available for future grants.

The Company did not grant any options to purchase shares of common stock during the three months ended March 31, 2023.

As of March 31, 2023, there was $18.4 million of total unrecognized compensation expense related to unvested stock options, which is expected to be recognized over a weighted-average period of 1.93 years.

During 2018, the Company granted restricted stock awards to employees under the 2018 Plan. The restricted stock awards vested ratably over a four-year period from the date of grant. The fair value of each restricted stock award was the estimated fair value of the common stock on the date of grant. All restricted stock awards were fully vested as of January 2022.

During 2021, the Company awarded restricted stock units to employees and certain nonemployee board members under the 2021 Plan. During the three months ended March 31, 2023, the Company awarded restricted stock units covering an aggregate of 2,413,230 shares of common stock. The fair value of each restricted stock unit is estimated

based on the fair value of the Company's common stock on the date of the grant. The restricted stock units vest over the requisite service period, which range between one and four years from the date of the grant, subject to the continued employment of the employees and service of the nonemployee board members.

As of March 31, 2023, there was $105.3 million of total unrecognized compensation expense related to unvested restricted stock units, which is expected to be recognized over a weighted-average period of 2.33 years.

In April 2021, the Company’s board of directors adopted, and in May 2021 its stockholders approved, the 2021 Employee Stock Purchase Plan (ESPP), which became effective on May 28, 2021. The ESPP authorizes the issuance of shares of common stock pursuant to purchase rights granted to "eligible employees". A total of 3,797,245 shares of common stock have been reserved for future issuance under the ESPP, in addition to any annual automatic evergreen increases in the number of shares of common stock reserved for future issuance under the ESPP. The price at which common stock is purchased under the ESPP is equal to 85% of the fair market value of a share of common stock on the first or last day of the offering period, whichever is lower. Eligible employees can contribute up to 15% of their eligible compensation. Offering periods are generally 6 months long.

As of March 31, 2023, a total of 3,766,959 shares of the Company's common stock were available for future issuance under the ESPP.

The fair value of the ESPP offering during the three months ended March 31, 2023 was estimated at the date of the offering using the Black-Scholes option-pricing model with the following assumptions: (i) expected term of 0.5 years, (ii) expected volatility of 62.02%, (iii) risk-free interest rate of 4.77% and (iv) expected dividend yield of 0%.

As of March 31, 2023, the total unrecognized compensation expense related to the ESPP was $0.4 million, which is expected to be amortized over the next 3 months.

The following table summarizes the stock-based compensation expense for stock options, restricted stock units and ESPP granted to employees and nonemployee board members that was recorded in the Company’s condensed consolidated statements of operations and comprehensive loss (in thousands):


	Three Months Ended March 31,
	2023		2022
Technology and development	$	1,569	$	830
Selling and marketing		2,437		1,311
General and administrative		4,597		3,354
Total stock-based compensation expense	$	8,603	$	5,495