Net Income (Loss) Per Share Attributable to Common Stockholders - Summary of Potential Shares of Common Stock Excluded from Computation of Diluted Net Income (Loss) Per Share Attributable to Common Stockholders (Details) - shares	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Class A Common Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings (loss) per share (in shares)	1,929,417	0	0
Issuance of common stock reserved for charitable donation (in shares)	500,000
Class A Common Stock | Convertible preferred stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings (loss) per share (in shares)	0	0	0
Class A Common Stock | Outstanding stock options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings (loss) per share (in shares)	141,782	0	0
Class A Common Stock | Unvested RSUs
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings (loss) per share (in shares)	606,971	0	0
Class A Common Stock | Purchase rights committed under the ESPP
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings (loss) per share (in shares)	1,180,664	0	0
Class A Common Stock | Shares subject to repurchase from early exercised stock options and restricted stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings (loss) per share (in shares)	0	0	0
Class B Common Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings (loss) per share (in shares)	0	3,541,878	189,138,776
Class B Common Stock | Convertible preferred stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings (loss) per share (in shares)	0	0	152,665,804
Class B Common Stock | Outstanding stock options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings (loss) per share (in shares)	0	3,541,878	34,170,489
Class B Common Stock | Unvested RSUs
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings (loss) per share (in shares)		0	0
Class B Common Stock | Purchase rights committed under the ESPP
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings (loss) per share (in shares)		0	0
Class B Common Stock | Shares subject to repurchase from early exercised stock options and restricted stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings (loss) per share (in shares)	0	0	2,302,483