The following table presents the classification of stock-based compensation for the periods indicated:

	Three Months Ended July 31,				Six Months Ended July 31,
	2022		2021		2022		2021
	(in thousands)
Stock-based compensation:
Cost of revenue	$	362	$	359	$	711	$	682
Research and development		17,883		11,525		35,034		22,719
Selling, general and administrative		8,664		7,488		18,205		14,813
Total stock-based compensation	$	26,909	$	19,372	$	53,950	$	38,214

As of July 31, 2022, approximately $1.7 million of stock-based compensation expense was accrued and reflected under accrued and other current liabilities in the condensed consolidated balance sheets. Total unrecognized compensation cost related to unvested stock options at July 31, 2022 was $21.7 million and is expected to be recognized over a weighted-average period of 2.20 years. Total unrecognized compensation cost related to unvested restricted stock units at July 31, 2022 was $189.2 million and is expected to be recognized over a weighted-average period of 2.30 years. In April 2022, the Company’s Compensation Committee of the Board of Directors approved the acceleration of vesting of 35,703 shares of unvested equity awards associated with the departure of Mr. Casey Eichler, who was the Company’s Chief Financial Officer until March 2022. As a result, there was approximately $1.7 million of additional stock-based compensation expense, net related to the departure recognized in fiscal year 2023.

The following table sets forth the weighted-average assumptions used to estimate the fair value of stock options and employee stock purchase plan awards for the periods indicated:

	Three Months Ended July 31,					Six Months Ended July 31,
	2022		2021			2022			2021
Stock Options:
Volatility		—		50	%		—			51	%
Risk-free interest rate		—		0.85	%		—			0.98	%
Expected term (years)		—	5.06				—		5.27
Dividend yield		—		0	%		—			0	%
Employee stock purchase plan awards:
Volatility		—		—			89	%		61	%
Risk-free interest rate		—		—			0.86	%		0.06	%
Expected term (years)		—		—		0.5			0.5
Dividend yield		—		—			0	%		0	%

The following table summarizes stock option activities for the period indicated:

	Option Outstanding
										Weighted-
								Total Intrinsic		Average
						Weighted-		Value Of		Remaining		Aggregate
				Weighted-		Average		Options		Contractual		Intrinsic
				Average		Grant-date		Exercised		Term		Value
	Shares			Exercise Price		Fair Value		(in thousands)		(in years)		(in thousands)
Outstanding at January 31, 2022		619,322		$	40.08
Granted		—			—		—
Exercised		(64,395	)		32.20			$	3,878
Forfeited		(6,323	)		45.88
Expired		(518	)		10.89
Outstanding at July 31, 2022		548,086			40.97					4.68		$	25,303
Exercisable at July 31, 2022		386,400		$	43.27						3.59	$	16,853

The intrinsic value of options outstanding and exercisable is calculated based on the difference between the fair market value of the Company’s ordinary shares on the reporting date and the exercise price. The closing price of the Company’s ordinary shares on July 29, 2022 was $86.55, as reported by The NASDAQ Global Market. The intrinsic value of exercised options is calculated based on the difference between the fair market value of the Company’s ordinary shares on the exercise date and the exercise price.

The following table summarizes restricted stock unit activities for the period indicated:

				Weighted-
				Average
				Grant-Date
	Shares			Fair Value
Unvested at January 31, 2022		2,651,135		$	85.41
Granted		708,985			85.87
Vested		(995,693	)		68.42
Forfeited		(61,722	)		100.28
Unvested at July 31, 2022		2,302,705		$	92.87

As of July 31, 2022, the aggregate intrinsic value of unvested restricted stock units was $199.3 million.