Our Amended and Restated Certificate of Incorporation, as amended and restated in May 2019, authorizes the issuance of 1.0 billion shares of Class A common stock and 94.1 million shares of Class B common stock, and 10.0 million shares of preferred stock, each at a par value per share of $0.00002. Holders of Class A common stock are entitled to one vote per share and holders of Class B common stock are entitled to 10 votes per share. Preferred stockholders, do not have voting rights.

As of March 31, 2020 and December 31, 2019, 24.2 million and 33.9 million shares of Class B common stock were issued and outstanding, respectively. As of March 31, 2020 and December 31, 2019, 71.8 million and 61.0 million shares of Class A common stock were issued and outstanding, respectively. As of both March 31, 2020 and December 31, 2019, no shares of preferred stock were issued and outstanding.

In March 2011, our stockholders approved our 2011 Equity Incentive Plan ("2011 Plan") which allows for the issuance of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, and restricted stock unit awards ("RSUs") to employees, directors, and consultants of the Company. Options granted under our 2011 Plan are exercisable for shares of our Class B common stock.

As of both March 31, 2020 and December 31, 2019, there were 23.6 million shares of Class B common stock reserved for issuance under the 2011 Plan. As of both March 31, 2020 and December 31, 2019, there were no shares of Class B common stock available for issuance pursuant to future grants under the 2011 Plan.

In May 2019, in conjunction with our IPO, our Board and stockholders approved our 2019 Equity Incentive Plan (the "2019 Plan") which allows for the issuance of incentive stock options, non-statutory stock options, stock appreciation rights, RSUs, performance-based stock awards, and other forms of equity compensation, which are collectively referred to as stock awards. Additionally, the 2019 Plan provides for the grant of performance cash awards. Options are exercisable for shares of our Class A common stock. No further awards will be issued under the 2011 Plan.

As of March 31, 2020 and December 31, 2019, there were 19.2 million shares and 14.4 million shares of Class A common stock reserved for issuance under the 2019 Plan, respectively. As of March 31, 2020 and December 31, 2019, there were 16.0 million and 12.4 million Class A common stock available for issuance under the 2019 Plan, respectively.

In May 2019, in conjunction with our IPO, our Board and stockholders approved the Employee Stock Purchase Plan ("ESPP"). The ESPP allows eligible employees to purchase shares of our Class A common stock through payroll deductions of up to 15% of their eligible compensation, subject to a maximum of $25,000 per calendar year.

As of March 31, 2020 and December 31, 2019, there were 3.5 million shares and 2.5 million shares of Class A common stock reserved for issuance under the ESPP, respectively. As of March 31, 2020 and December 31, 2019, there were 3.1 million shares and 2.2 million shares of Class A common stock available for future issuance under the ESPP, respectively.

Options granted under the 2011 Plan are exercisable for Class B common stock and generally expire within 10 years from the date of grant and generally vest over four years, at the rate of 25% on the first anniversary of the date of grant and ratably on a monthly basis over the remaining 36-month period thereafter based on continued service.

Options granted under the 2019 Plan are exercisable for Class A common stock and generally expire within 10 years from the date of grant and generally vest over four years, at the rate of 25% on the first anniversary of the date of grant and ratably on a monthly basis over the remaining 36-month period thereafter based on continued service. Forfeitures are recognized as they occur.



	Shares		Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value
	(in thousands)				(in years)	(in thousands)
Outstanding at December 31, 2019	11,269		$	4.68	7.3	$	173,471
Granted	—		—
Exercised	(1,107	)	2.68
Cancelled/forfeited	(61	)	6.94
Outstanding at March 31, 2020	10,101		$	4.89	7.2	$	142,692
Vested and exercisable at March 31, 2020	6,443		$	3.00	6.4	$	102,947

The weighted average grant-date fair value for options granted to employees during the three months ended March 31, 2019 was $5.10. There were no options granted during the three months ended March 31, 2020.

We estimate the fair value of stock options on the date of grant using the Black-Scholes option-pricing model. Each of the Black-Scholes inputs is subjective and generally requires significant judgments to determine. We estimated the fair value of stock option awards using the Black-Scholes option pricing model with the following weighted-average assumptions:



	Three months ended March 31,
	2020	2019
Fair value of common stock	N/A	$10.32
Expected term (in years)	N/A	6.02
Risk-free interest rate	N/A	2.50%
Expected volatility	N/A	40.0%
Dividend yield	N/A	—%

As of March 31, 2020, total unrecognized stock-based compensation cost related to outstanding unvested stock options that are expected to vest was $16.2 million. This unrecognized stock-based compensation cost is expected to be recognized over a weighted-average period of approximately 2.58 years.

Certain stock options granted by the Company are exercisable at the date of grant, with unvested shares subject to repurchase by the Company in the event of voluntary or involuntary termination of employment of the stockholder. Such exercises are recorded as a liability on the accompanying Condensed Consolidated Balance Sheets and reclassified into equity as the options vest. As of March 31, 2020 and December 31, 2019, a total of 163,305 and 199,895 shares of Class B Common Stock were subject to repurchase by the Company at the lower of (i) the fair market value of such shares on the date of repurchase, or (ii) the original exercise price of such shares. The corresponding exercise value of approximately $0.7 million and $0.9 million as of March 31, 2020 and December 31, 2019, respectively, is recorded in other current liabilities and other liabilities on the accompanying Condensed Consolidated Balance Sheets.



	Three months ended March 31,
	2020
	(in thousands)
Beginning balance as of December 31, 2019	200
Early exercise of options	—
Vested	(37	)
Repurchased	—
Ending balance as of March 31, 2020	163

We began granting RSUs under the 2019 Plan during the fiscal year ended December 31, 2019. The fair value of RSUs is based on the grant date fair value and is expensed on a straight-line basis over the applicable vesting period. RSUs typically vest over four years, at the rate of 25% on the first anniversary of the vest date and ratably on a quarterly basis over the remaining 36-month period thereafter, based on continued service. Forfeitures are recognized as they occur.



	Shares		Weighted- Average Grant Date Fair Value Per Share
	(in thousands)
Nonvested RSUs as of December 31, 2019	1,641		$	20.07
Granted	1,072		20.03
Vested	—
Cancelled/forfeited	(11	)	20.04
RSUs outstanding as of March 31, 2020	2,702		$	20.04

During the three months ended March 31, 2020, we recognized stock-based compensation expense related to RSUs of $4.1 million. There was no stock-based compensation expense recognized related to RSUs during the three months ended March 31, 2019.

As of March 31, 2020, total unrecognized stock-based compensation cost related to non-vested RSUs was $47.9 million. This unrecognized stock-based compensation cost is expected to be recognized over a weighted-average period of approximately 3.16 years.

In March 2020, the Company granted a maximum total of 87,918 shares of performance-based restricted stock unit awards ("PSUs") to certain employees of the company, pursuant to the Company’s 2019 Equity Incentive Plan. The PSUs represents the right of the employees to be issued on a future date, one (1) share of Class A common stock for each RSU received that will vest on the applicable vesting date.

The issuance of the underlying shares occurs upon approval by the Compensation Committee of the Board of Directors based on the level of achievement of certain Company and individual performance goals set by the Compensation Committee for year ending December 31, 2020 and their continued service with the Company. Subject to employees’ continuous service with the Company through each vesting date, 25% of the number of RSUs credited to them upon certification of achievement will vest on February 15, 2021, May 15, 2021, August 15, 2021, and November 15, 2021, respectively.

As of the three months ended March 31, 2020, none of these performance conditions have been set or met. We expect to record stock-based compensation related to these PSUs once it is considered probable that the performance conditions will be met.

The ESPP allows eligible employees to purchase shares of our common stock through payroll deductions of up to 15% of their eligible compensation. The ESPP provides for six-month offering periods, commencing in May and November of each year. At the end of each offering period employees are able to purchase shares at 85% of the lower of the fair market value of our Class A common stock on the first trading day of the offering period or on the date of purchase.

We estimate the fair value of shares to be issued under the ESPP on the first day of the offering period using the Black-Scholes valuation model. The inputs to the Black-Scholes option pricing model are our stock price on the first date of the offering period, the risk-free interest rate, the estimated volatility of our stock price over the term of the offering period, the expected term of the offering period and the expected dividend rate. Stock-based compensation expense related to the ESPP is recognized on a straight-line basis over the offering period. Forfeitures are recognized as they occur.



	Three months ended March 31,
	2020	2019
Fair value of common stock	$6.02	N/A
Expected term (in years)	0.50	N/A
Risk-free interest rate	1.59%	N/A
Expected volatility	43.0%	N/A
Dividend yield	—%	N/A

During the three months ended March 31, 2020, we withheld $2.2 million in contributions from employees, and recognized $0.7 million in stock-based compensation expense related to the ESPP. No contributions were withheld, and no stock-based compensation expense was recognized related to the ESPP in the three months ended March 31, 2019. No common stock was issued under the ESPP in the three months ended March 31, 2020.



	Three months ended March 31,
	2020		2019
	(in thousands)
Stock-based compensation expense by caption:
Cost of revenue	$	615	$	144
Research and development	1,671		432
Sales and marketing	1,483		369
General and administrative	2,560		522
Total	$	6,329	$	1,467