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Stock-Based Awards (Tables)

12 Months Ended

Dec. 31, 2017

Option Awards

The following table summarizes option award activity for the year ended December 31, 2017 (in thousands, except per share data and years):

	Number of Shares Underlying Options			Weighted-Average Exercise Price Per Share		Weighted-Average Remaining Contractual Life (Years)		Total Intrinsic Value
Outstanding at December 31, 2016		2,310		$	8.84
Granted		1,275			36.26
Exercised		(444	)		3.64
Forfeited or Cancelled		(291	)		16.16
Outstanding at December 31, 2017		2,850			21.16		8.01		20,802
Vested and exercisable at December 31, 2017		1,009		$	6.72		6.14	$	16,128

Schedule of Stock Options Valuation Assumptions

The fair value of options granted is estimated at the date of grant using the Black-Scholes-Merton option-pricing model with the following assumptions for the periods presented:

		Stock Options
		Year Ended December 31,
	2017		2016		2015
Risk-free interest rate	1.8% – 2.2%		1.1% – 2.1%		1.2% – 1.6%
Expected dividends yield	None		None		None
Expected volatility	52.2% – 59.1%		40.8% – 49.5%		41.5% – 43.4%
Weighted-average expected life	6.08		5.78		4.31
Weighted-average fair value of options granted	$	19.15	$	9.60	$	3.12

Summary of Unvested Shares Related to Early Exercise of Common Stock Activity

The following table summarizes activity of unvested shares related to early exercise of our common stock for the year ended December 31, 2017 (in thousands, except per share data):

	Shares Outstanding
	Number of Shares			Weighted-Average Exercise Price per Share
Outstanding at December 31, 2016		118		$	3.30
Issued		1			4.71
Vested		(69	)		2.59
Repurchased		(2	)		3.19
Outstanding at December 31, 2017		48			4.32

Schedule of Employee Stock Purchase Plan Valuation Assumptions

The fair value of the ESPP options granted is estimated at the start of the offering period using the Black-Scholes-Merton option-pricing model with the following assumptions for the periods presented:

	Employee Stock Purchase Plan
	Year Ended December 31,
	2017	2016
Risk-free interest rate	0.7% – 1.1%	0.4%
Expected term	0.5 years	0.5 years
Expected volatility	66.5% – 71.2%	61.8%

Summary of Stock-Based Compensation Expense

Stock-Based Compensation Expense

The following table presents the detail of stock-based compensation expense amounts included in our consolidated statements of operations for the periods indicated (in thousands):

	Year Ended
	December 31,
	2017		2016		2015
Cost of revenue	$	231	$	96	$	31
Research and development expense		2,431		983		305
Sales and marketing expense		3,113		1,289		692
General and administrative expense		1,653		397		150
Total stock-based compensation expense	$	7,428	$	2,765	$	1,178

Restricted Stock Units

Summary of Restricted Stock Units

The following table summarizes activity for restricted stock units for the year ended December 31, 2017 (in thousands, except per share data):

	Shares Outstanding
	Number of Shares		Weighted-Average Grant Date Fair Value
Outstanding at December 31, 2016		—	$	—
Granted		12		46.53
Outstanding at December 31, 2017		12		46.53