We maintain two equity incentive plans: the 2009 Equity Incentive Plan (the 2009 Plan) and the 2015 Equity Incentive Plan (the 2015 Plan). The 2015 Plan serves as the successor to our 2009 Plan and provides for grants of incentive stock options to our employees and non-statutory stock options, stock appreciation rights, restricted stock, RSUs, performance stock awards, performance cash awards, and other forms of stock awards to our employees, directors and consultants. Outstanding awards granted under our 2009 Plan will remain subject to the terms of our 2009 Plan and applicable award agreements, until such outstanding awards that are stock options are exercised, terminated or expired by their terms. Our equity awards generally vest over a two to four year period and expire no later than ten years from the date of grant.

We initially reserved 27,000,000 shares of our common stock for issuance under our 2015 Plan. The number of shares reserved for issuance under our 2015 Plan increases automatically on the first day of each fiscal year, for a period of not more than ten years, commencing on February 1, 2016, in an amount equal to 5% of the total number of shares of our capital stock outstanding as of the immediately preceding January 31 (the Evergreen Increase). In March 2022, our board of directors approved an amendment and restatement of the 2015 Plan to clarify the effect of our change to a 52/53 week fiscal year in September 2019 on the Evergreen Increase.

We net-share settle equity awards held by certain employees by withholding shares upon vesting to satisfy tax withholding obligations. The shares withheld to satisfy employee tax withholding obligations are returned to our 2015 Plan and will be available for future issuance. Payments for employees’ tax obligations to the tax authorities are recognized as a reduction to additional paid-in capital and reflected as a financing activity in our consolidated statements of cash flows.

Our 2015 Employee Stock Purchase Plan was amended and restated in fiscal 2020 (2015 ESPP). A total of 3,500,000 shares of common stock was initially reserved for issuance under the 2015 ESPP and an additional 5,000,000 shares of common stock were added in connection with the amendment and restatement. The number of shares reserved for issuance under our 2015 ESPP increases automatically on the first day of February of each of 2016 through 2025, in an amount equal to the lesser of (i) 1% of the total number of shares of our capital stock outstanding as of the immediately preceding January 31, and (ii) 3,500,000 shares of common stock.

Our board of directors (or a committee thereof) has the authority to establish the length and terms of the offering periods and purchase periods and the purchase price of the shares of common stock which may be purchased under the plan. The current offering terms allow eligible employees to purchase shares of our common stock at a discount through payroll deductions of up to 30% of their eligible compensation, subject to a cap of 3,000 shares on any purchase date, a dollar cap of $7,500 per purchase period (instituted in February 2019), or $25,000 in any calendar year (as determined under applicable tax rules). The current terms also allow for a 24-month offering period beginning March 16th and September 16th of each year, with each offering period consisting of four 6 month purchase periods, subject to a reset provision. Further, currently, on each purchase date, eligible employees may purchase our common stock at a price per share equal to 85% of the lesser of the fair market value of our common stock (1) on the first trading day of the applicable offering period or (2) the purchase date.

Under the reset provision currently authorized, if the closing stock price on the offering date of a new offering falls below the closing stock price on the offering date of an ongoing offering, the ongoing offering would terminate immediately following the purchase of ESPP shares on the purchase date immediately preceding the new offering and participants in the terminated ongoing offering would automatically be enrolled in the new offering (ESPP reset), resulting in a modification charge to be recognized over the new offering period. During fiscal 2020 and 2021, multiple ESPP resets resulted in total modification charges of $13.6 million and $23.8 million to be recognized over their new offering periods. There was no ESPP reset during fiscal 2022.

During fiscal 2020, 2021 and 2022, we recognized $24.5 million, $25.8 million and $35.4 million, of stock-based compensation expense related to our 2015 ESPP. At the end of fiscal 2022, total unrecognized stock-based compensation cost related to our 2015 ESPP was $9.9 million, which is expected to be recognized over a weighted-average period of approximately 0.8 years.


	Options Outstanding
	Number of Shares	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value (in thousands)
Balance at the end of fiscal 2021	18,558,974	$	9.60	4.3	$	251,503

Options exercised	(5,954,724)	8.15
Options forfeited/canceled	(335,312)	11.50
Balance at the end of fiscal 2022	12,268,938	$	10.25	3.5	$	198,266
Vested and exercisable at the end of fiscal 2022	11,565,305	$	10.73	3.2	$	180,978

The aggregate intrinsic value of options vested and exercisable at the end of fiscal 2022 is calculated based on the difference between the exercise price and the closing price of $26.38 of our common stock on the last day of fiscal 2022. The aggregate intrinsic value of options exercised during fiscal 2020, 2021 and 2022 was $106.6 million, $118.8 million and $105.1 million.

During fiscal 2020, 2021 and 2022, we recognized $15.8 million, $8.6 million and $7.7 million, of stock-based compensation expense related to stock options. At the end of fiscal 2022, total unrecognized employee stock-based compensation cost related to outstanding options was $7.5 million, which is expected to be recognized over a weighted-average period of 1.6 years.

The fair value of stock options granted to employees and to be purchased under ESPP is estimated on the grant date using the Black-Scholes option pricing model. This valuation model for stock-based compensation expense requires us to make assumptions and judgments about the variables used in the calculation including the fair value of the underlying common stock, expected term, the expected volatility of the common stock, a risk-free interest rate and expected dividend yield. The assumptions used for the periods presented are as follows:


	Fiscal Year Ended
	2020	2021	2022
Employee Stock Options
Expected term (in years)	n/a	5.65	n/a
Expected volatility	n/a	52.07%	n/a
Risk-free interest rate	n/a	0.3%	n/a
Dividend rate	n/a	—	n/a
Fair value of common stock	n/a	$15.79	n/a
Employee Stock Purchase Plan
Expected term (in years)	0.5 - 2.0	0.5 - 2.0	0.5 - 2.0
Expected volatility	42% - 47%	52% - 113%	44% - 61%
Risk-free interest rate	1.7% - 2.5%	0.1% - 0.4%	0.1% - 0.2%
Dividend rate	—	—	—
Fair value of common stock	$17.76 - $20.87	$9.07 - $15.26	$23.63 - $26.69

Expected Term—The expected term represents the period that our stock-based awards are expected to be outstanding. The expected term assumptions were determined based on the vesting terms, exercise terms and contractual lives of the options and ESPP purchase rights.

Risk-Free Interest Rate—The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant for zero-coupon U.S. Treasury notes with maturities approximately equal to the expected term of the stock option grants and ESPP purchase rights.

A summary of the RSU and PRSU activity under our equity incentive plans and related information is as follows:


	Number of RSUs and PRSUs Outstanding	Weighted-Average Grant Date Fair Value		Aggregate Intrinsic Value (in thousands)
Unvested balance at the end of fiscal 2021	30,830,082	$	15.77	$	712,657
Granted	17,173,968	23.42

Vested	(12,955,468)	17.07
Forfeited	(6,335,704)	16.60

Unvested balance at the end of fiscal 2022	28,712,878	$	19.53	$	757,446

During fiscal 2022, we granted 1,600,373 shares of PRSUs, at a target percentage of 100%, with both performance and service vesting conditions payable in common stock, from 0% to 150% of the target number granted, contingent upon the degree to which the performance condition is met. A total of 2,028,355 shares were earned at the end of fiscal 2022 based on the performance condition achieved and these shares are subject to service conditions through the vesting periods.

During fiscal 2020, 2021 and 2022, we recognized $161.8 million, $199.1 million and $242.1 million in stock-based compensation expense related to RSUs and PRSUs. At the end of fiscal 2022, total unrecognized employee compensation cost related to unvested RSUs and PRSUs was $503.2 million, which is expected to be recognized over a weighted-average period of 2.7 years.

A summary of the restricted stock activity under our 2015 Plan and related information is as follows:


	Number of Restricted Stock Outstanding	Weighted- Average Grant Date Fair Value		Aggregate Intrinsic Value (in thousands)
Unvested balance at the end of fiscal 2021	557,836	$	19.06	$	12,903

Vested	(440,687)	18.78
Forfeited	(62,172)	20.22
Unvested balance at the end of fiscal 2022	54,977	$	20.02	$	1,450

All unvested shares of restricted stock are subject to cancellation to the extent vesting conditions are not met. The aggregate fair value of restricted stock that vested during fiscal 2020, 2021 and 2022 was $24.2 million, $18.3 million and $10.4 million.

During fiscal 2020, 2021 and 2022, we recognized $24.6 million, $9.3 million and $1.8 million in stock-based compensation expense related to restricted stock. At the end of fiscal 2022, total unrecognized employee compensation cost related to unvested restricted stock was not material, which is expected to be recognized over a weighted-average period of approximately 0.1 years.


	Fiscal Year Ended
	2020		2021		2022
Cost of revenue—product	$	3,732	$	4,001	$	6,334
Cost of revenue—subscription services	14,403		14,979		21,240
Research and development	107,658		117,220		142,264
Sales and marketing	67,560		65,248		71,439
General and administrative	33,352		40,896		45,686
Total stock-based compensation expense	$	226,705	$	242,344	$	286,963