The following table summarizes the components of stock-based compensation expense in the condensed consolidated statements of operations (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2022		2021		2022		2021

Cost of revenue	$	4,982	$	2,945	$	13,609	$	9,749
Research and development	4,818		5,678		25,113		15,876
Sales and marketing	3,948		4,391		13,528		12,486
General and administrative	10,283		7,952		30,688		19,198
	$	24,031	$	20,966	$	82,938	$	57,309


	Outstanding Options
	Number of Shares	Weighted Average Exercise Price		Remaining Contractual Life (Years)	Aggregate Intrinsic Value

					(in thousands)












Balances at December 31, 2021	10,737,295	$	21.23	5.2	$	60,304

Exercised	(468,821)	7.52
Forfeited	(42,742)	6.97
Expired	(1,229,091)	30.38
Balances at September 30, 2022	8,996,641	20.77		4.8	45,054
Vested and expected to vest at September 30, 2022	8,985,005	20.78		4.8	44,901
Exercisable at September 30, 2022	8,598,209	$	21.46	4.7	39,364

Stock Options - During the three and nine months ended September 30, 2022, we recognized $1.2 million and $6.7 million of stock-based compensation expense for stock options, respectively. During the three and nine months ended September 30, 2021, we recognized $2.7 million and $10.0 million of stock-based compensation expense for stock options, respectively. We did not grant options in the three and nine months ended September 30, 2022 and 2021.

As of September 30, 2022 and December 31, 2021, we had unrecognized compensation expense related to unvested stock options of $0.8 million and $6.2 million, respectively. This expense is expected to be recognized over the remaining weighted-average period of 0.5 years and 0.9 years, respectively. Cash received from stock options exercised totaled $3.6 million and $62.1 million for the nine months ended September 30, 2022 and 2021, respectively.


	Number of Awards Outstanding	Weighted Average Grant Date Fair Value













Unvested Balance at December 31, 2021	8,367,664	$	20.52
Granted	4,945,001	19.69
Vested	(2,328,713)	17.59
Forfeited	(900,629)	21.76
Unvested Balance at September 30, 2022	10,083,323	19.99

Stock Awards - The estimated fair value of restricted stock units (“RSUs”) and performance stock units (“PSUs”) is based on the fair value of our Class A common stock on the date of grant. During the three and nine months ended September 30, 2022, we recognized $18.4 million and $64.4 million of stock-based compensation expense for stock awards, respectively. During the three and nine months ended September 30, 2021, we recognized $15.8 million and $40.6 million of stock-based compensation expense for stock awards, respectively.

As of September 30, 2022 and December 31, 2021, we had $155.2 million and $114.9 million of unrecognized stock-based compensation expense related to unvested stock awards, expected to be recognized over a weighted average period of 2.1 and 2.3 years, respectively.

The following table presents the stock activity for the nine months ended September 30, 2022, and the total number of shares available for grant under our stock plans as of September 30, 2022:


						Plan Shares Available for Grant
Balances at December 31, 2021						24,146,784
Added to plan						8,384,460
Granted						(4,981,732)

Cancelled/Forfeited						2,062,177
Expired						(1,196,565)
Balances at September 30, 2022						28,415,124

During the nine months ended September 30, 2022 and 2021, we recognized $11.2 million and $4.5 million of stock-based compensation expense for the 2018 Employee Stock Purchase Plan, respectively. We issued 759,744 and 1,945,305 shares in the nine months ended September 30, 2022 and 2021, respectively. During the nine months ended September 30, 2022 and 2021, we added an additional 12,055,792 shares and 1,902,572 shares, respectively. There were 13,840,716 shares and 2,544,668 shares available for issuance as of September 30, 2022 and 2021, respectively.

As of September 30, 2022 and December 31, 2021, we had $10.4 million and $9.8 million of unrecognized stock-based compensation expense, expected to be recognized over a weighted average period of 1.1 years and 0.5 years, respectively.