Common Stock and Stockholders’ Equity

Employee Stock Purchase Plan—The Company’s board of directors adopted, and the Company’s stockholders approved, the Company’s 2014 Employee Stock Purchase Plan (the “ESPP”), which became effective in December 2014. The ESPP initially reserved and authorized the issuance of up to 1,000,000 shares of common stock. The ESPP provides that the number of shares reserved and available for issuance under the ESPP automatically increases each April, beginning on April 1, 2015, by the lesser of 500,000 shares, 1% of the number of the Company’s common stock shares issued and outstanding on the immediately preceding March 31, or such lesser number of shares as determined by the Company’s board of directors. For the nine months ended December 31, 2018, 82,851 shares of common stock were purchased under the ESPP. For the nine months ended December 31, 2017, 101,493 shares of common stock were purchased under the ESPP. Stock-based compensation expense recognized related to the ESPP was $1.0 million and $0.6 million for the three months ended December 31, 2018 and 2017, respectively, and $2.5 million and $1.6 million for the nine months ended December 31, 2018 and 2017, respectively. As of December 31, 2018, there were 2,346,386 shares available for issuance under the ESPP.

2008 Equity Incentive Plan—The Company’s board of directors adopted, and the Company’s stockholders approved, the 2008 Equity Incentive Plan (the “2008 Plan”) in February 2008. The 2008 Plan was terminated in connection with the Company’s initial public offering, and accordingly, no shares are available for future issuance under this plan. The 2008 Plan continues to govern outstanding awards granted thereunder.

2014 Equity Incentive Plan—The Company’s board of directors adopted, and the Company’s stockholders approved, the Company’s 2014 Equity Incentive Plan (the “2014 Plan”), which became effective in December 2014. The 2014 Plan serves as the successor to the Company’s 2008 Plan. The 2014 Plan initially reserved and authorized the issuance of 5,000,000 shares of the Company’s common stock. Additionally, shares not issued or subject to outstanding grants under the 2008 Plan upon its termination became available under the 2014 Plan, resulting in a total of 5,184,878 available shares under the 2014 Plan as of the effective date of the 2014 Plan. Pursuant to the terms of the 2014 Plan, any shares subject to outstanding stock options or other stock awards under the 2008 Plan that (i) expire or terminate for any reason prior to exercise or settlement, (ii) are forfeited because of the failure to meet a contingency or condition required to vest such shares or otherwise return to the Company or (iii) are reacquired, withheld (or not issued) to satisfy a tax withholding obligation in connection with an award or to satisfy the purchase price or exercise price of a stock award will become available for issuance pursuant to awards granted under the 2014 Plan. The 2014 Plan provides that the number of shares reserved and available for issuance under the plan automatically increases each April 1, beginning on April 1, 2015, by 5% of the outstanding number of shares of the Company’s common stock shares issued and outstanding on the immediately preceding March 31, or such lesser number of shares as determined by the Company’s board of directors. As of December 31, 2018, there were 11,662,042 shares available for issuance under the 2014 Plan.

The following table summarizes the Company’s stock option and RSU award activities for the nine months ended December 31, 2018 (in thousands, except exercise price, contractual term and fair value information):



	Options Outstanding							RSUs Outstanding
	Number of Shares		Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value		Number of Shares		Weighted- Average Grant Date Fair Value		Weighted- Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding - April 1, 2018	3,215		$	22.79	6.7	$	165,041	2,079		$	42.31	2.7	$	154,071
Stock options granted	307		98.32
RSUs granted								748		96.28
Stock options exercised	(552	)	20.89			41,555
RSUs vested								(688	)	41.38
Stock options canceled/forfeited	(96	)	52.74
RSUs canceled/forfeited								(248	)	50.84
Outstanding - December 31, 2018	2,874		$	30.22	6.1	$	150,780	1,891		$	62.88	2.7	$	153,149

Stock-Based Compensation Expense—Aggregate stock-based compensation expense for employees and nonemployees was $14.8 million and $9.9 million for the three months ended December 31, 2018 and 2017, respectively, and $39.6 million and $29.8 million for the nine months ended December 30, 2018 and 2017, respectively.

Cost of revenue, research and development, sales and marketing, and general and administrative expenses were as follows (in thousands):



	Three Months Ended December 31,				Nine Months Ended December 31,
	2018		2017		2018		2017
Cost of revenue	$	934	$	587	$	2,522	$	1,716
Research and development	4,322		2,959		11,443		9,100
Sales and marketing	6,222		3,933		17,040		12,114
General and administrative	3,286		2,454		8,619		6,848
Total stock-based compensation expense	$	14,764	$	9,933	$	39,624	$	29,778

As of December 31, 2018, unrecognized stock-based compensation cost related to outstanding unvested stock options was $18.1 million, which is expected to be recognized over a weighted-average period of approximately 2.2 years. As of December 31, 2018, unrecognized stock-based compensation cost related to outstanding unvested stock units was $109.1 million, which is expected to be recognized over a weighted-average period of approximately 2.7 years.