Convertible Preferred Stock, Stockholders’ Equity (Deficit) and Equity Incentive Plan - Schedule of Stock by Class Reserved for Future Issuance (Details) - shares	Jan. 31, 2020	Jan. 31, 2019
Class of Stock [Line Items]
Number of shares available for future issuance (in shares)	60,911,996	189,578,369
Convertible preferred stock
Class of Stock [Line Items]
Number of shares available for future issuance (in shares)	0	152,665,804
Stock options
Class of Stock [Line Items]
Number of shares available for future issuance (in shares)	16,833,009	35,064,465
RSUs
Class of Stock [Line Items]
Number of shares available for future issuance (in shares)	1,964,668	0
ESPP
Class of Stock [Line Items]
Number of shares available for future issuance (in shares)	1,323,662	0
2011 and 2019 Plan
Class of Stock [Line Items]
Number of shares available for future issuance (in shares)	33,604,587	1,848,100
2019 Employee Stock Purchase Plan | ESPP
Class of Stock [Line Items]
Number of shares available for future issuance (in shares)	7,186,070	0