In connection with our IPO, our board of directors resolved not to make future grants under our 2011 Stock Option and Grant Plan (the “2011 Plan”). The 2011 Plan will continue to govern outstanding awards granted thereunder. The 2011 Plan provided for the grant of qualified incentive stock options and nonqualified stock options or other awards such as restricted stock awards (“RSAs”) to our employees, officers, directors and outside consultants.

In July 2015, our board of directors adopted and our stockholders approved our 2015 Equity Incentive Plan (the “2015 Plan”). We initially reserved 800,000 shares of our common stock for the issuance of awards under the 2015 Plan plus the number of shares of common stock reserved for issuance under the 2011 Plan at the time the 2015 Plan became effective. The 2015 Plan also provides that (i) any shares subject to awards granted under the 2011 Plan that would have otherwise returned to the 2011 Plan (such as upon the expiration or termination of a stock award prior to vesting) will be added to, and available for issuance under, the 2015 Plan and (ii) the number of shares reserved and available for issuance under the 2015 Plan automatically increases each January 1, beginning on January 1, 2016, by 4% of the outstanding number of shares of our common stock on the immediately preceding December 31 (known as the “evergreen” provision) or such lesser number of shares as determined by our board of directors. Additionally, on October 8, 2015, our board of directors amended the 2015 Plan to reserve an additional 1,500,000 shares of our common stock for issuance of inducement awards.

Stock-based compensation expense for restricted stock units (“RSUs”), performance-based restricted stock units (“PSUs”), stock options, purchase rights issued under our employee stock purchase plan (“ESPP”) and earnout consideration and key employee consideration shares related to acquisitions was classified in the accompanying consolidated statements of operations as follows:


	Year Ended December 31,
		2024		2023		2022
		(in thousands)
Stock-based compensation expense:
Cost of revenue		$	12,208	$	11,005	$	10,367
Research and development		37,566		39,183		49,940
Sales and marketing		28,718		30,350		31,217
General and administrative		29,469		31,098		28,378
Total stock-based compensation expense		$	107,961	$	111,636	$	119,902

Our Compensation Committee adopted and approved the performance goals, targets and payout formulas for our 2024, 2023 and 2022 bonus plans, including permitting our executive officers and certain other employees the opportunity to receive payment of their earned bonuses in the form of common stock (in lieu of cash). For the years ended December 31, 2024, 2023, and 2022, we recognized stock-based compensation expense related to such bonuses in the amount of $0.9 million, $1.6 million and $1.0 million, respectively, based on the probable expected performance against the pre-established corporate financial objectives as of December 31, 2024, 2023 and 2022. For employees, including executive officers, who elect to receive their bonuses in the form of common stock (in lieu of cash), the payouts are expected to be made in the form of fully vested stock awards in the first quarter of the following year pursuant to our 2015 Equity Incentive Plan, as amended. The number of shares underlying such awards is determined by dividing the dollar value of the actual bonus award payment by the closing price per share of our common stock on the date of grant.


	Shares	Weighted- Average Grant Date Fair Value
Unvested balance as of December 31, 2021	2,778,877	$	74.40
Granted	2,327,216	86.78
Vested	(1,481,333)	69.80
Forfeited	(623,317)	85.93
Unvested balance as of December 31, 2022	3,001,443	83.88
Granted	2,304,140	48.83		(1)
Vested	(1,453,713)	73.29		(1)
Forfeited	(1,137,444)	67.93		(1)
Unvested balance as of December 31, 2023	2,714,426	66.40		(1)
Granted	2,563,810	53.99
Vested	(1,462,352)	64.78
Forfeited	(962,649)	62.16
Unvested balance as of December 31, 2024	2,853,235	$	57.25

(1) The weighted average grant date fair values for RSUs and PSUs granted, vested and forfeited during fiscal year 2023, as well as the weighted average grant date fair value of awards unvested as of December 31, 2023 have been revised from prior period disclosures. Refer to Note 20, Immaterial Correction of an Error, for further information.

In January 2024, our Compensation Committee awarded 279,570 PSUs that required the achievement of net annualized recurring revenue (“Net ARR”) and Adjusted EBITDA targets for the 2024 full-year to earn any payout. Net ARR is defined as the change in the annual value of all recurring revenue related to contracts in place at year end. In addition, the portion of the PSUs that are earned would be capped at a maximum of 200% of the target level payout and if certain net ARR or Adjusted EBITDA goals were not met, no PSUs will be earned. The PSUs have a performance period of one year and the earned PSUs will vest in three equal installments following each of the first, second and third anniversary of the vesting commencement date, subject to the participant’s continuous service as of each such date. The 2024 target level attainment was 50% and in the year ended December 31, 2024, we recorded $3.4 million of stock-based compensation expense related to these PSUs based on that level of attainment of the performance criteria.

In July 2024, our Compensation Committee awarded 19,605 PSUs that required the achievement of certain milestones related to the integration of Noetic. The PSUs have three measurement and vesting dates through September 15, 2025, subject to the participant's continuous service as of each such date. If the milestones are not achieved, no PSUs will be earned. In the year ended December 31, 2024, we recorded $0.6 million of stock-based compensation expense related to these PSUs based on estimated achievement of the performance criteria.


	Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2021	1,411,387	$	10.74		$	150,951
Granted	—	—
Exercised	(479,223)	6.92			$	20,764
Forfeited/cancelled	(38)	21.15
Outstanding as of December 31, 2022	932,126	12.70			$	19,837
Granted	—	—
Exercised	(215,856)	14.14			$	6,519
Forfeited/cancelled	—	—
Outstanding as of December 31, 2023	716,270	12.26			$	32,115
Granted	—	—
Exercised	(133,182)	11.75			$	5,013
Forfeited/cancelled	(450)	7.73
Outstanding as of December 31, 2024	582,638	12.38		1.2	$	16,225
Vested and exercisable as of December 31, 2024	582,638	$	12.38	1.2	$	16,225

The number of shares reserved and available for issuance under our 2015 Employee Stock Purchase Plan (“ESPP”) automatically increases each January 1, beginning on January 1, 2016, by 1% of the outstanding number of shares of our common stock on the immediately preceding December 31 (known as the “evergreen” provision) or such lesser number of shares as determined by our board of directors. As of December 31, 2024, the shares of common stock authorized to be issued under the ESPP totaled 5,370,139 and there were 3,076,461 shares of common stock available for grant.

Under the ESPP, employees may set aside up to 15% of their gross earnings, on an after-tax basis, to purchase our common shares at a discounted price, which is calculated at 85% of the lesser of: (i) the market value of our common stock at the beginning of each offering period and (ii) the market value of our common stock on the applicable purchase date.

The fair value of shares issued under our ESPP is estimated on the grant date using the Black-Scholes option pricing model. The expected term represents the term from the first day of the offering period to the purchase dates within each offering period. The expected volatility is based on the historical volatilities of our own common stock. The risk-free interest rate is based on U.S. Treasury zero-coupon securities with maturities consistent with the estimated expected term. We have not paid dividends on our common stock nor do we expect to pay dividends in the foreseeable future.


	Year Ended December 31,
	2024	2023	2022
Expected term (in years)	0.5 - 1.0	0.5 - 1.0	0.5 - 1.0
Expected volatility	37 - 47%	47 - 68%	37 - 57%
Risk-free interest rate	4.0 – 5.4%	4.5 – 5.5%	0.1 – 4.0%
Expected dividend yield	—	—	—
Grant date fair value per share	$9.96 – $17.25	$11.70 – $20.07	$15.50 –$29.58


	September 13, 2024			March 15, 2024			September 15, 2023			March 15, 2023			September 15, 2022	March 15, 2022

Common shares issued	144,445			147,445			152,419			177,886			218,314	80,747
Purchase prices	$29.08			$33.78 and $39.78			$33.78			$34.71			$45.31	$67.59 and $81.37
Aggregate proceeds	$	4.2	million	$	5.0	million	$	5.1	million	$	6.1	million	$6.2 million	$5.7 million