Equity Incentive Plans (Tables)

12 Months Ended

Jan. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Stock Option Activity Under Equity Incentive Plans and Related Information

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

	Options Outstanding
	Number of Shares		Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
						(in thousands)
Balance as of January 31, 2017	56,840,189		$	7.15	7.0	$	315,502
Options granted	1,000,000		14.92
Options exercised	(8,814,019	)	2.79
Options cancelled/forfeited	(2,666,221	)	13.91
Balance as of January 31, 2018	46,359,949		$	7.75	6.3	$	574,224
Vested and exercisable as of January 31, 2018	28,990,955		$	5.30	5.7	$	430,325

Summary of Estimate Fair Value of Employee Stock Options and Employee Purchase Plan

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

	Year Ended January 31,
	2016		2017		2018
Employee Stock Options
Expected term (in years)	6.0 - 7.4		6.1		6.1
Expected volatility	48% - 52%		44	%	47	%
Risk-free interest rate	1.5% - 1.9%		1.3% - 1.5%		1.9	%
Dividend rate	—		—		—
Fair value of common stock	$13.94 - $19.68		$10.37 - $14.52		$12.84
Employee Stock Purchase Plan
Expected term (in years)	0.4 - 1.9		0.5 - 2.0		0.5 - 2.0
Expected volatility	49	%	41	%	35% - 39%
Risk-free interest rate	0.1% - 0.7%		0.5% - 0.9%		0.9% - 1.4%
Dividend rate	—		—		—

Schedule of Share-based Compensation, Restricted Stock Units Award Activity

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

	Number of Restricted Stock Units Outstanding	Weighted-Average Grant Date Fair Value		Aggregate Intrinsic Value
				(in thousands)
Unvested balance as of January 31, 2017	8,783,024	$	13.06	$	99,863
Granted	15,779,364	12.16
Vested	(5,277,679)	12.30
Forfeited	(1,602,063)	11.88
Unvested balance of January 31, 2018	17,682,646	$	12.60	$	356,117

Summarizes the Components of Stock-Based Compensation

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

	Year Ended January 31,
	2016		2017		2018
Cost of revenue—product	$	276	$	601	$	1,630
Cost of revenue—support	2,388		5,639		9,050
Research and development	31,135		63,495		71,229
Sales and marketing	16,966		34,317		47,687
General and administrative	7,460		12,616		21,077
Total stock-based compensation expense	$	58,225	$	116,668	$	150,673