Convertible Preferred Stock, Stockholders’ Equity (Deficit) and Equity Incentive Plan - Additional Information (Details)					1 Months Ended	12 Months Ended
	Jan. 15, 2021 USD ($) $ / shares shares	Apr. 30, 2019 USD ($) shares	Apr. 23, 2019 USD ($) $ / shares shares	Apr. 18, 2019 shares	Apr. 30, 2019 USD ($) vote shares	Jan. 31, 2021 USD ($) $ / shares shares	Jan. 31, 2020 USD ($) $ / shares shares	Jan. 31, 2019 USD ($) $ / shares shares	Nov. 30, 2018 vote $ / shares shares	Jan. 31, 2018 USD ($) shares
Class of Stock [Line Items]
Convertible preferred stock, shares outstanding (in shares)						0	0	152,665,804		152,665,804
Conversion of convertible preferred stock to common stock upon initial public offering | $							$ 0	$ 159,552,000		$ 159,552,000
Convertible preferred stock, shares issued (in shares)						0	0
Undesignated preferred stock shares authorized (in shares)						200,000,000	200,000,000
Undesignated referred stock par value (in dollars per share) | $ / shares						$ 0.001	$ 0.001
Common stock, conversion features, term						6 months
Initial offering period						15 years
Common stock, par value (in dollars per share) | $ / shares						$ 0.001	$ 0.001
Stock options outstanding (in shares)						9,239,504	16,833,009
Weighted average grant date fair value of options for employees (in dollars per share) | $ / shares							$ 25.17	$ 6.28
Expected unrecognized stock-based compensation expenses related to outstanding unvested stock options | $						$ 46,700,000
Number of shares available for future issuance (in shares)						68,708,474	60,911,996
Number of purchase periods | vote					4
Fair value of donated shares | $						$ 23,312,000
Other Assets, Non-current
Class of Stock [Line Items]
Capitalized deferred offering costs within other assets, non-current | $								$ 2,400,000
RSUs
Class of Stock [Line Items]
Unrecognized stock-based compensation expenses | $						$ 734,600,000
Unrecognized stock-based compensation excepted to be recognized over a weighted-average period						2 years 8 months 12 days
Number of shares available for future issuance (in shares)						4,510,730	1,964,668
Purchase rights committed under the ESPP
Class of Stock [Line Items]
Unrecognized stock-based compensation expenses | $						$ 31,900,000
Unrecognized stock-based compensation excepted to be recognized over a weighted-average period						4 months 24 days
Number of shares available for future issuance (in shares)						724,883	1,323,662
Maximum number of shares per employee (in shares)					3,000
Consecutive offering period					27 months
Stock options
Class of Stock [Line Items]
Unrecognized stock-based compensation excepted to be recognized over a weighted-average period						1 year 4 months 24 days
Number of shares available for future issuance (in shares)						9,239,504	16,833,009
2019 Plan
Class of Stock [Line Items]
Shares reserved for issuance, percentage		5.00%			5.00%
2019 Employee Stock Purchase Plan | Purchase rights committed under the ESPP
Class of Stock [Line Items]
Number of shares available for future issuance (in shares)						9,648,574	7,186,070
Percent of outstanding stock, maximum					1.00%
Number of additional shares allowable under the plan (in shares)					7,500,000
Initial public offering
Class of Stock [Line Items]
Convertible preferred stock, shares outstanding (in shares)			152,665,804
Conversion of convertible preferred stock to common stock upon initial public offering | $			$ 159,600,000
Undesignated preferred stock shares authorized (in shares)			200,000,000
Undesignated referred stock par value (in dollars per share) | $ / shares			$ 0.001
Over-Allotment Option
Class of Stock [Line Items]
Deferred offering costs, reclassified to stockholders' equity | $		$ 6,400,000
Class A Common Stock
Class of Stock [Line Items]
Common stock number of votes per share | vote									1
Common stock, shares authorized (in shares)						2,000,000,000	2,000,000,000		320,000,000
Common stock, par value (in dollars per share) | $ / shares						$ 0.001			$ 0.001
Issuance of common stock reserved for charitable donation (in shares)						94,844	500,000
Class A Common Stock | Held For Charitable Contributions
Class of Stock [Line Items]
Fair value of donated shares | $						$ 23,300,000
Class A Common Stock | Purchase rights committed under the ESPP
Class of Stock [Line Items]
Percentage of purchase price of common stock to fair market value of common stock on offering or purchase date					85.00%
ESPP excess rate purchase right, value | $					$ 25,000
Shares issued of common stock (in shares)						923,553	490,268
Class A Common Stock | 2011 Plan
Class of Stock [Line Items]
Other shares authorized (in shares)		24,300,889			24,300,889
Class A Common Stock | 2019 Plan
Class of Stock [Line Items]
Number of shares authorized (in shares)		58,300,889			58,300,889
Number of additional shares authorized under the plan (in shares)		34,000,000			34,000,000
Class A Common Stock | 2019 Employee Stock Purchase Plan | Purchase rights committed under the ESPP
Class of Stock [Line Items]
Number of shares available for future issuance (in shares)		9,000,000			9,000,000
Class A Common Stock | Initial public offering
Class of Stock [Line Items]
Shares issued (in shares)			9,911,434
Conversion of convertible preferred stock to common stock upon initial public offering (in shares)			426,223
Class A Common Stock | Over-Allotment Option
Class of Stock [Line Items]
Shares issued (in shares)	735,294			3,130,435
Shares issued, price per share (in dollars per share) | $ / shares	$ 340.00		$ 36.00
Aggregate proceeds from shares issued | $	$ 1,980,000,000.0		$ 447,900,000
Class A Common Stock | Private Placement
Class of Stock [Line Items]
Shares issued (in shares)			2,777,777
Aggregate proceeds from shares issued | $			$ 100,000,000.0
Class A Common Stock | Follow-On Public Offering
Class of Stock [Line Items]
Shares issued (in shares)	5,882,353
Class B Common Stock
Class of Stock [Line Items]
Common stock number of votes per share | vote									10
Common stock, shares authorized (in shares)						300,000,000	300,000,000		300,000,000
Common stock, par value (in dollars per share) | $ / shares						$ 0.001			$ 0.001
Class B Common Stock | Initial public offering
Class of Stock [Line Items]
Conversion of convertible preferred stock to common stock upon initial public offering (in shares)			152,665,804