CONDENSED CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY (DEFICIT) - USD ($)	Total	Redeemable Convertible Preferred Stock, Series E	Redeemable Convertible Preferred Stock, Series F	Redeemable Convertible Preferred Stock, Series G-1 And G-2	Class A and Class B Common Stock	Additional Paid-in Capital	Additional Paid-in Capital Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment
Beginning balance (in shares) at Jan. 31, 2018	138,947,468
Beginning balance at Jan. 31, 2018	$ 472,626,000
Increase (Decrease) in Temporary Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201817Member
Issuance of redeemable convertible preferred stock (in shares)		134,018	29,227,556
Issuance of redeemable convertible preferred stock		$ 1,000,000	$ 437,227,000
Ending balance (in shares) at Jan. 31, 2019	168,309,042
Ending balance at Jan. 31, 2019	$ 910,853,000
Beginning balance (in shares) at Jan. 31, 2018					45,327,678
Beginning balance at Jan. 31, 2018	$ (131,892,000)				$ 5,000	$ 11,863,000	$ 377,000	$ (24,000)	$ (143,736,000)	$ (377,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)	5,292,551				5,292,551
Issuance of common stock upon exercise of stock options	$ 2,264,000				$ 1,000	2,263,000
Repurchase of early exercised stock options and restricted common stock (in shares)					(6,010,592)
Repurchases and retirement of common stock in connection with issuer tender offers	(29,644,000)				$ (1,000)				(29,643,000)
Vesting of early exercised stock options and restricted common stock	1,807,000					1,807,000
Issuance of restricted common stock (in shares)					950,000
Stock-based compensation	22,986,000					22,986,000
Other comprehensive income	40,000							40,000
Net loss	(178,028,000)								(178,028,000)
Ending balance (in shares) at Jan. 31, 2019					45,559,637
Ending balance at Jan. 31, 2019	(312,467,000)				$ 5,000	39,296,000		16,000	(351,784,000)
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of redeemable convertible preferred stock (in shares)			1,612,230
Issuance of redeemable convertible preferred stock			$ 24,121,000
Stock-based compensation	$ 1,500,000
Ending balance (in shares) at Jan. 31, 2020	169,921,272
Ending balance at Jan. 31, 2020	$ 936,474,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)	9,735,006				9,735,006
Issuance of common stock upon exercise of stock options	$ 27,526,000				$ 1,000	27,525,000
Repurchase of early exercised stock options and restricted common stock (in shares)					(520,557)
Vesting of early exercised stock options and restricted common stock	5,791,000					5,791,000
Issuance of restricted common stock (in shares)					16,700
Issuance of common stock in connection with an acquisition (in shares)					661,635
Issuance of common stock in connection with an acquisition	4,749,000					4,749,000
Stock-based compensation	77,979,000					77,979,000
Other comprehensive income	200,000							200,000
Net loss	(348,535,000)								(348,535,000)
Ending balance (in shares) at Jan. 31, 2020					55,452,421
Ending balance at Jan. 31, 2020	$ (544,757,000)				$ 6,000	155,340,000		216,000	(700,319,000)
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of redeemable convertible preferred stock (in shares)				12,349,827
Issuance of redeemable convertible preferred stock				$ 478,573,000
Conversion of redeemable convertible preferred stock to common stock upon initial public offering (in shares)	(182,271,099)
Conversion of redeemable convertible preferred stock to common stock upon initial public offering	$ (1,415,047,000)
Ending balance (in shares) at Jan. 31, 2021	0
Ending balance at Jan. 31, 2021	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of redeemable convertible preferred stock to common stock upon initial public offering (in shares)					182,271,099
Conversion of redeemable convertible preferred stock to common stock upon initial public offering	1,415,047,000				$ 18,000	1,415,029,000
Issuance of common stock, new issues (in shares)					36,366,666
Issuance of common stock new issues	$ 4,242,284,000				$ 4,000	4,242,280,000
Issuance of common stock upon exercise of stock options (in shares)	13,798,741				13,798,741
Issuance of common stock upon exercise of stock options	$ 53,671,000					53,671,000
Exercise of common stock warrants (in shares)					32,241
Repurchase of early exercised stock options and restricted common stock (in shares)					(40,000)
Vesting of restricted stock units (in shares)					36,436
Vesting of early exercised stock options and restricted common stock	5,592,000					5,592,000
Stock-based compensation	303,513,000					303,513,000
Other comprehensive income	223,000							223,000
Net loss	(539,102,000)								(539,102,000)
Ending balance (in shares) at Jan. 31, 2021					287,917,604
Ending balance at Jan. 31, 2021	$ 4,936,471,000				$ 28,000	$ 6,175,425,000		$ 439,000	$ (1,239,421,000)