Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2017

Schedule of Common Stock Reserved for Future Issuance

As of December 31, 2017, shares of common stock reserved for future issuance related to outstanding equity awards, warrants, and employee equity incentive plans were as follows (in thousands):



		December 31, 2017
Stock options outstanding		4,047
Restricted stock units outstanding		2,033
Shares available for future grant under 2014 Plan		7,300
Shares available for future issuance under ESPP		1,371
Common stock warrants outstanding		13
Total shares of common stock reserved		14,764

Schedule of Stock Option Activities

A summary of the Company’s stock option activity during the year ended December 31, 2017 is as follows (in thousands, except years and per share data):



	Number of Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value ⁽¹⁾
Outstanding as of December 31, 2016	5,556		$	5.23
Options granted	619		18.11
Options exercised	(1,986	)	3.04
Options forfeited or expired	(142	)	12.83
Outstanding as of December 31, 2017	4,047		$	8.00	6.4	68,334
Vested and expected to vest as of December 31, 2017	4,047		8.00		6.4	68,334
Exercisable as of December 31, 2017	2,911		6.20		5.6	54,380


(1) The aggregate intrinsic value amounts are computed based on the difference between the exercise price of the stock options and the fair market value of the Company’s common stock of $24.88 per share as of December 31, 2017 for all in-the-money stock options outstanding.

Following is additional information pertaining to the Company’s stock option activity (in thousands, except per share data):



	Year Ended December 31,
	2017		2016		2015
Weighted average grant date fair value per share of options granted	$	8.81	$	4.50	$	2.38
Intrinsic value of options exercised ⁽¹⁾	33,820		5,865		3,233
Total fair value of options vested during the period	7,296		3,813		4,824
Cash received from options exercised	6,047		4,286		1,268


(1) Intrinsic value of options exercised is the difference between the fair market value of the Company’s common stock at the time of exercise and the exercise price paid.

Schedule of RSU Activities

A summary of RSU activity during the year ended December 31, 2017 is as follows (in thousands, except years and per share data):



	Number of Shares		Weighted Average Grant Date Fair Value Per Share
Outstanding as of December 31, 2016	2,019		$	7.65
RSUs granted	1,176		18.29
RSUs vested and released	(971	)	8.85
RSUs forfeited	(191	)	11.42
Outstanding as of December 31, 2017	2,033		$	12.81

Following is additional information pertaining to the Company’s RSU activity (in thousands, except per share data):



	Year Ended December 31,
	2017		2016		2015
Weighted average grant date fair value per share of RSUs granted	$	18.29	$	9.71	$	5.10
Total fair value of RSUs vested during the period	21,161		10,706		2,907

Schedule of Stock-based Compensation Expense

Stock-based compensation expenses for the years ended December 31, 2017, 2016 and 2015 were as follows (in thousands):



	Year Ended December 31,
	2017		2016		2015
Cost of revenue	$	2,202	$	1,375	$	866
Research and development	3,042		2,059		1,790
Sales and marketing	4,364		2,363		1,800
General and administrative ⁽¹⁾	5,735		3,846		3,274
Total stock-based compensation	$	15,343	$	9,643	$	7,730


(1)	Effective December 2017, the Company’s former Chief Executive Officer and President resigned from his position and became the Executive Chairman of the Board. Due to this substantive change in status, certain of his stock option and RSU awards were modified which resulted in incremental stock based compensation expense of approximately $1.0 million.

Schedule of Unrecognized Compensation Expense

As of December 31, 2017, unrecognized stock-based compensation expense by award type and their expected weighted-average recognition periods are summarized in the following table (in thousands, except years).



	Stock Option		RSU		ESPP
Unrecognized stock-based compensation expense	$	10,703	$	26,401	$	670
Weighted-average amortization period	2.5 years		2.8 years		0.4 years

Schedule of Valuation Assumptions, Stock Option

The weighted-average assumptions used to value stock options and purchase rights under the ESPP granted during the years ended December 31, 2017, 2016 and 2015 were as follows:



Stock Options	Year Ended December 31,
	2017	2016	2015
Expected term (years)	5.9	5.7	6.1
Volatility	49%	46%	49%
Risk-free interest rate	2.1%	1.4%	1.6%
Dividend yield	—	—	—

Schedule of Valuation Assumptions for Employee Stock Purchase Plan



ESPP	Granted In
	November 2017	May 2017	November 2016	May 2016	November 2015	May 2015
Expected term (years)	0.5	0.5	0.5	0.5	0.5	0.5
Volatility	36%	43%	42%	58%	54%	43%
Risk-free interest rate	1.4%	1.0%	0.6%	0.4%	0.3%	0.1%
Dividend yield	—	—	—	—	—	—