Net Loss Per Share - Computation of Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2019
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net loss	$ (84,634)	$ (125,656)	$ (154,309)
Weighted-average number of shares used in computing net loss per share, basic and diluted (shares)	29,308	27,520	16,358
Net loss per share, basic and diluted (in usd per share)	$ (2.89)	$ (4.57)	$ (9.43)
Class A Common Stock
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net loss	$ (9,426)	$ (14,903)	$ (18,305)
Weighted-average number of shares used in computing net loss per share, basic and diluted (shares)	3,264	3,264	1,941
Net loss per share, basic and diluted (in usd per share)	$ (2.89)	$ (4.57)	$ (9.43)
Class B Common Stock
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net loss	$ (75,208)	$ (110,753)	$ (136,004)
Weighted-average number of shares used in computing net loss per share, basic and diluted (shares)	26,044	24,256	14,417
Net loss per share, basic and diluted (in usd per share)	$ (2.89)	$ (4.57)	$ (9.43)