Net Loss Per Share Attributable to Common Stockholders - Antidilutive (Details) - shares shares in Thousands	12 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from diluted net loss per share (in shares)	16,515	23,194	158,685
Shares of common stock issuable upon conversion of redeemable convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from diluted net loss per share (in shares)	0	0	131,268
Shares of common stock issuable upon conversion of redeemable convertible preferred stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from diluted net loss per share (in shares)	0	0	336
Shares of common stock subject to repurchase from outstanding stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from diluted net loss per share (in shares)	548	984	546
RSUs and PSUs subject to future vesting
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from diluted net loss per share (in shares)	8,449	6,063	0
Shares of common stock issuable from stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from diluted net loss per share (in shares)	6,646	14,689	26,535
Share purchase rights under the employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from diluted net loss per share (in shares)	872	1,458	0