Common Stock and Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2021

Common Stock and Stockholders'Equity

Summary of stock option activity under the Plan

Activity under the Plans is as follows (in thousands, except share and per share amounts and years):

				Weighted-
		Weighted-		Average
	Number of	Average		Remaining	Aggregate
	Shares	Exercise		Contractual	Intrinsic
	Outstanding	Price		Life in Years	Value
Balance at December 31, 2020	5,826,685	$	17.19	5.31	$	1,064,944
Stock option grants	3,688	$	107.06	N/A
Stock options exercised	(1,237,399)	$	9.62	N/A	$	(212,993)
Stock options forfeited	(44,031)	$	14.47	N/A
Balance at March 31, 2021	4,548,943	$	19.41	5.69	$	738,498
Vested or expected to vest at March 31, 2021	4,548,943	$	19.41	5.69	$	738,498
Exercisable at March 31, 2021	3,700,190	$	16.88	5.33	$	610,040

Assumptions used for estimate of fair value of options

	Quarter Ended March 31,
	2021		2020
Volatility		57.02% - 57.49%		46.1% – 47.9%
Expected term (in years)		4.1		4.3
Risk-free interest rate		0.31% - 0.51%		0.87% - 1.64%
Dividend yield		0		0
Weighted-average fair value of underlying stock options	$	$107.06	$	42.06

Schedule of activity under the RSUs

Activity under the RSUs is as follows:

		Weighted-Average
		Grant Date
	RSUs	Fair Value Per RSU
Balance at December 31, 2020	3,550,595	$	162.11
Granted	402,210	$	218.88
Vested and issued	(708,798)	$	102.94
Forfeited	(115,243)	$	184.40
Balance at March 31, 2021	3,128,764	$	181.99
Vested and unissued at March 31, 2021	13,755	$	50.90
Non-vested at March 31, 2021	3,115,009	$	182.57

Schedule of activity under the PSUs

Activity under the PSUs is as follows:

		Weighted-Average
		Grant Date
	Shares	Fair Value Per PSU
Balance at December 31, 2020	429,319	$	76.60
Granted	516,031	$	131.67
Vested and issued	(268,201)	$	74.33
Balance at March 31, 2021	677,149	$	119.47
Vested and unissued at March 31, 2021	0	$	0
Non-vested at March 31, 2021	677,149	$	119.47

Components of operating expense charged for compensation cost expense

Total compensation costs for stock-based awards were recorded as follows (in thousands):

	Quarter Ended
	March 31,
	2021		2020
Cost of revenue (exclusive of depreciation and amortization, which is shown separately)	$	2,362	$	0
Advertising and marketing		5,082		1,259
Sales		21,167		2,919
Technology and development		26,726		2,104
General and administrative		30,963		12,033
Total stock-based compensation expense (1)	$	86,300	$	18,315