In January 2015, our board of directors adopted the 2015 Equity Incentive Plan (2015 Plan), which became effective prior to the completion of our initial public offering (IPO). Awards granted under the 2015 Plan may be (i) incentive stock options, (ii) nonstatutory stock options, (iii) restricted stock units, (iv) restricted stock awards or (v) stock appreciation rights, as determined by our board of directors at the time of grant. Generally, our restricted stock units vest over four years and, (a) for employee new hire restricted stock unit grants, twenty-five percent vest one year from the vesting commencement date and continue to vest 1/16th per quarter thereafter; or (b) for employee refresh restricted stock unit grants, 1/16th per quarter vest from the vesting commencement date. As of October 31, 2021, 26,849,605 shares were reserved for future issuance under the 2015 Plan.

In January 2015, our board of directors adopted the 2015 Employee Stock Purchase Plan (2015 ESPP), which became effective prior to the completion of our IPO. The 2015 ESPP allows eligible employees to purchase shares of our Class A common stock at a discount of up to 15% through payroll deductions of their eligible compensation, subject to any plan limitations. The 2015 ESPP provides for 24-month offering periods beginning March 16 and September 16 of each year, and each offering period consists of four six-month purchase periods.

On each purchase date, eligible employees may purchase our stock at a price per share equal to 85% of the lesser of (1) the fair market value of our stock on the offering date or (2) the fair market value of our stock on the purchase date. In the event the price is lower on the last day of any purchase price period, in addition to using that price as the basis for that purchase period, the offering period resets and the new lower price becomes the new offering price for a new 24 month offering period. As of October 31, 2021, 6,382,506 shares were reserved for future issuance under the 2015 ESPP.

The following table summarizes the stock option activity under the equity incentive plans and related information:


	Shares Subject to Options Outstanding					Weighted- Average
				Weighted-		Remaining
				Average Exercise		Contractual Life		Aggregate
	Shares			Price		(Years)		Intrinsic Value
								(in thousands)
Balance as of January 31, 2021		6,617,037		$	10.77		3.77	$	48,098
Options granted		—			—
Options exercised		(314,720	)		7.60
Options forfeited/cancelled		—			—
Balance as of October 31, 2021		6,302,317		$	10.93		3.07	$	93,985
Vested and expected to vest as of October 31, 2021		6,243,569		$	10.84		3.03	$	93,649
Exercisable as of October 31, 2021		5,132,047		$	8.83		2.19	$	87,283

As of October 31, 2021, there was $0.5 million of unrecognized stock-based compensation expense related to outstanding stock options granted to employees that is expected to be recognized over a weighted-average period of 1.24 years.

The following table summarizes the restricted stock unit activity under the equity incentive plans and related information:


	Number of			Weighted-
	Restricted			Average
	Stock Units			Grant Date
	Outstanding			Fair Value
Unvested balance - January 31, 2021		14,330,678		$	17.68
Granted		10,117,269			24.06
Vested		(5,285,619	)		19.61
Forfeited/cancelled		(3,337,538	)		19.22
Unvested balance - October 31, 2021		15,824,790		$	20.78

As of October 31, 2021, there was $306.5 million of unrecognized stock-based compensation expense related to outstanding restricted stock units granted to employees that is expected to be recognized over a weighted-average period of 2.83 years.

We use performance-based incentives for certain employees, including our named executive officers, to achieve our annual financial and operational objectives, while making progress towards our longer-term strategic and growth goals. During the nine months ended October 31, 2021, we recognized stock-based compensation expense related to the Fiscal 2021 and Fiscal 2022 Executive Bonus Plans in the amount of $3.2 million and $10.7 million, respectively. The unrecognized compensation expense related to the ungranted and unvested Fiscal 2022 Executive Bonus Plan is $4.1 million, based on the expected performance against the pre-established corporate financial objectives as of October 31, 2021, which is expected to be recognized over a remaining weighted-average period of less than one year. The payouts of the Fiscal 2022 Executive Bonus Plan are expected to be made in the form of fully vested restricted stock units in the first quarter of fiscal year 2023.

As of October 31, 2021, there was $15.1 million of unrecognized stock-based compensation expense related to the 2015 ESPP that is expected to be recognized over the remaining term of the respective offering periods.

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


	Three Months Ended				Nine Months Ended
	October 31,				October 31,
	2021		2020		2021		2020
Cost of revenue	$	4,786	$	4,731	$	15,009	$	13,673
Research and development		17,712		14,581		49,791		46,139
Sales and marketing		13,872		10,619		38,342		31,364
General and administrative		9,219		7,903		28,365		24,262
Total stock-based compensation	$	45,589	$	37,834	$	131,507	$	115,438