Note 10. Stock-Based Compensation

2015 Equity Incentive Plan

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). A total of 12,200,000 shares of Class A common stock was initially reserved for issuance pursuant to future awards under the 2015 Plan. Additionally, any shares subject to outstanding awards under our 2006 Equity Incentive Plan (2006 Plan) or 2011 Equity Incentive Plan (2011 Plan) that are cancelled or repurchased subsequent to the 2015 Plan’s effective date will be returned to the pool of shares reserved for issuance under the 2015 Plan. 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. Options and restricted stock units generally vest 25% one year from the vesting commencement date and (a) in the case of options, 1/48^th per month thereafter, and (b) in the case of restricted stock units, 1/16th per quarter thereafter. As of April 30, 2015, 16,331,626 shares were reserved for future issuance under the 2015 Plan.

2015 Employee Stock Purchase Plan

In January 2015, our board of directors adopted the 2015 Employee Stock Purchase Plan, which became effective prior to the completion of our IPO. A total of 2,500,000 shares of Class A common stock was initially reserved for issuance under the 2015 ESPP. The 2015 ESPP allows eligible employees to purchase shares of our Class A common stock at a discount through payroll deductions of up to 15% of their eligible compensation, subject to any plan limitations. Except for the initial offering period, the 2015 ESPP provides for 24-month offering periods beginning March 16 and September 16 of each year, and each offering period will consist of four six-month purchase periods. The initial offering period began January 23, 2015, and will end on March 15, 2017.

On each purchase date, eligible employees will 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. As of April 30, 2015, 3,696,550 shares were reserved for future issuance under the 2015 ESPP.

Early Exercises of Stock Options

Prior to our IPO, certain employees and directors exercised stock options prior to vesting with the approval of our board of directors. The unvested shares are subject to a repurchase right held by us at the original purchase price. Early exercises of options are not deemed to be substantive exercises for accounting purposes, and accordingly, amounts received for early exercises are initially recorded in other liabilities and are reclassified to common stock and additional paid-in capital as the underlying shares vest. As of April 30, 2015 and January 31, 2015, we had $98,000 and $286,000, respectively, in liabilities and 67,499 and 113,541 unvested shares subject to repurchase related to early exercises of stock options.

Stock Options

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

	Shares Subject to Options Outstanding					Weighted-Average
	Shares Subject to			Weighted-		Remaining
	Outstanding			Average Exercise		Contractual Life		Aggregate
	Options			Price		(Years)		Intrinsic Value
								(in thousands)
Balance as of January 31, 2015		17,465,571		$	5.67		7.80	$	229,713
Options granted		342,980			17.54
Option exercised		(350,096	)		3.09
Options forfeited/cancelled		(563,225	)		6.92
Balance as of April 30, 2015		16,895,230		$	5.92		7.60	$	190,236
Vested and expected to vest as of April 30, 2015		16,628,973		$	5.85		7.58	$	188,405
Exercisable as of April 30, 2015		8,924,686		$	3.50		6.98	$	121,735

The aggregate intrinsic value of options vested and expected to vest and exercisable as of April 30, 2015 is calculated based on the difference between the exercise price and the current fair value of our common stock. The aggregate intrinsic value of exercised options for the three months ended April 30, 2015 and 2014 was $5.3 million and $11.0 million, respectively. The aggregate estimated fair value of stock options granted to employees that vested during the three months ended April 30, 2015 and 2014 was $6.1 million and $4.4 million, respectively. The weighted-average grant date fair value of options granted to employees during the three months ended April 30, 2015 and 2014 was $7.70 and $8.66 per share, respectively.

As of April 30, 2015, there was $34.7 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 2.65 years.

Restricted Stock Units

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, 2015		4,939,709		$	15.66
Granted		2,673,044			17.54
Vested, net of shares withheld for employee payroll taxes		(348,962	)		17.77
Forfeited/cancelled, including shares withheld for employee payroll taxes		(430,831	)		17.17
Unvested balance - April 30, 2015		6,832,960		$	16.19

As of April 30, 2015, there was $101.1 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 3.47 years.

Restricted Stock

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

	Number of			Weighted-
	Restricted			Average
	Stock			Grant Date
	Outstanding			Fair Value
Unvested balance - January 31, 2015		172,661		$	9.60
Granted		23,364			17.54
Vested		(21,516	)		14.99
Forfeited/cancelled, including shares withheld for employee payroll taxes		(7,790	)		17.54
Unvested balance - April 30, 2015		166,719		$	9.65

In addition, in connection with our fiscal 2016 acquisitions, we issued 2,500 shares of restricted stock with a weighted-average grant date fair value of $17.54 per share during the three months ended April 30, 2015. This restricted stock was separately authorized by our board of directors, and did not reduce the number of shares available for future issuance under the 2015 Plan. All of these shares were still outstanding as of April 30, 2015.

As of April 30, 2015, there was $4.0 million of unrecognized stock-based compensation expense related to outstanding restricted stock granted to employees that is expected to be recognized over a weighted-average period of 2.19 years.

2015 ESPP and Other

As of April 30, 2015, there was $13.4 million of unrecognized stock-based compensation expense related to our 2015 ESPP that is expected to be recognized over the remaining term of the respective offering periods.

As of April 30, 2015, there was $1.4 million of unrecognized stock-based compensation related to 163,619 shares of contingently issuable common stock for certain bonus awards given in connection with our fiscal 2016 and 2015 acquisitions that is expected to be recognized over a weighted-average period of 2.14 years.

Stock-Based Compensation

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

	Three Months Ended
	April 30,
	2015		2014
Cost of revenue	$	851	$	226
Research and development		5,263		2,008
Sales and marketing		4,283		2,065
General and administrative		2,318		1,453
Net loss attributable to common stockholders	$	12,715	$	5,752

Determination of Fair Value

We estimated the fair value of employee stock options and ESPP purchase rights using a Black-Scholes option pricing model with the following assumptions:

	Three Months Ended
	April 30,
	2015					2014
Employee Stock Options
Expected term (in years)		6.0		-	6.1	5.7	-	6.1
Risk-free interest rate		1.6	%	-	1.7%				2.1%
Volatility		43	%	-	44%				49%
Dividend yield					0%			0%
Employee Stock Purchase Plan
Expected term (in years)	0.5			-	2.0				—
Risk-free interest rate		0.2	%	-	0.7%				—
Volatility		39	%	-	41%				—
Dividend yield					0%				—

The assumptions used in the Black-Scholes option pricing model were determined as follows:

Fair Value of Common Stock. Prior to our IPO in January 2015, our board of directors considered numerous objective and subjective factors to determine the fair value of our common stock at each grant date. These factors included, but were not limited to, (i) contemporaneous valuations of common stock performed by unrelated third-party specialists; (ii) the prices for our redeemable convertible preferred stock sold to outside investors; (iii) the rights, preferences and privileges of our redeemable convertible preferred stock relative to our common stock; (iv) the lack of marketability of our common stock; (v) developments in the business; and (vi) the likelihood of achieving a liquidity event, such as an IPO or a merger or acquisition, given prevailing market conditions.

Subsequent to the completion of our IPO, we use the market closing price for our Class A common stock as reported on the New York Stock Exchange.

Expected Term. The expected term represents the period that our share-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.

Expected Volatility. Since we do not have sufficient trading history of our common stock, the expected volatility was derived from the historical stock volatilities of several unrelated public companies within the same industry that we consider to be comparable to our business over a period equivalent to the expected term of the stock option grants and ESPP purchase rights.

Risk-free Interest Rate. The risk-free rate that we use is based on U.S. Treasury zero-coupon issues with remaining terms similar to the expected term on the options.

Dividend Yield. We have never declared or paid any cash dividends and do not plan to pay cash dividends in the foreseeable future, and, therefore, use an expected dividend yield of zero.