CONDENSED CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY (DEFICIT) - USD ($) $ in Thousands		Total	Common Stock		Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning balance (in shares) at Jan. 31, 2020		169,921,272
Beginning balance at Jan. 31, 2020		$ 936,474
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
Ending balance (in shares) at Jul. 31, 2020		182,271,099
Ending balance at Jul. 31, 2020		$ 1,415,047
Beginning balance (in shares) at Jan. 31, 2020			55,452,421
Beginning balance at Jan. 31, 2020		(544,757)	$ 6		$ 155,340	$ 216	$ (700,319)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)			6,844,642
Issuance of common stock upon exercise of stock options		20,736			20,736
Repurchase of early exercised stock options (in shares)			(40,000)
Vesting of early exercised stock options and restricted common stock		3,585			3,585
Stock-based compensation		39,385			39,385
Other comprehensive income (loss)		930				930
Net loss		(171,278)					(171,278)
Ending balance (in shares) at Jul. 31, 2020			62,257,063
Ending balance at Jul. 31, 2020		$ (651,399)	$ 6		219,046	1,146	(871,597)
Beginning balance (in shares) at Apr. 30, 2020		182,271,099
Beginning balance at Apr. 30, 2020		$ 1,415,047
Ending balance (in shares) at Jul. 31, 2020		182,271,099
Ending balance at Jul. 31, 2020		$ 1,415,047
Beginning balance (in shares) at Apr. 30, 2020			60,358,141
Beginning balance at Apr. 30, 2020		(604,046)	$ 6		188,416	1,495	(793,963)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)			1,898,922
Issuance of common stock upon exercise of stock options		9,864			9,864
Vesting of early exercised stock options and restricted common stock		2,386			2,386
Stock-based compensation		18,380			18,380
Other comprehensive income (loss)		(349)				(349)
Net loss		(77,634)					(77,634)
Ending balance (in shares) at Jul. 31, 2020			62,257,063
Ending balance at Jul. 31, 2020		$ (651,399)	$ 6		219,046	1,146	(871,597)
Beginning balance (in shares) at Jan. 31, 2021		0
Beginning balance at Jan. 31, 2021		$ 0
Ending balance (in shares) at Apr. 30, 2021		0
Ending balance at Apr. 30, 2021		$ 0
Beginning balance (in shares) at Jan. 31, 2021	[1]		287,917,604
Beginning balance at Jan. 31, 2021		$ 4,936,471	$ 28	[1]	6,175,425	439	(1,239,421)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		7,081,859
Ending balance (in shares) at Apr. 30, 2021			295,790,115
Ending balance at Apr. 30, 2021		$ 4,958,321	$ 30		6,400,566	366	(1,442,641)
Beginning balance (in shares) at Jan. 31, 2021		0
Beginning balance at Jan. 31, 2021		$ 0
Ending balance (in shares) at Jul. 31, 2021		0
Ending balance at Jul. 31, 2021		$ 0
Beginning balance (in shares) at Jan. 31, 2021	[1]		287,917,604
Beginning balance at Jan. 31, 2021		4,936,471	$ 28	[1]	6,175,425	439	(1,239,421)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)	[1]		11,056,645
Issuance of common stock upon exercise of stock options		65,668	$ 2	[1]	65,666
Issuance of common stock under employee stock purchase plan (in shares)	[1]		258,807
Issuance of common stock under employee stock purchase plan		26,398			26,398
Vesting of early exercised stock options and restricted common stock		423			423
Vesting of restricted stock units (in shares)	[1]		1,351,847
Stock-based compensation		328,242			328,242
Other comprehensive income (loss)		702				702
Net loss		(392,939)					(392,939)
Ending balance (in shares) at Jul. 31, 2021	[1]		300,584,903
Ending balance at Jul. 31, 2021		$ 4,964,965	$ 30	[1]	6,596,154	1,141	(1,632,360)
Beginning balance (in shares) at Apr. 30, 2021		0
Beginning balance at Apr. 30, 2021		$ 0
Ending balance (in shares) at Jul. 31, 2021		0
Ending balance at Jul. 31, 2021		$ 0
Beginning balance (in shares) at Apr. 30, 2021			295,790,115
Beginning balance at Apr. 30, 2021		$ 4,958,321	$ 30		6,400,566	366	(1,442,641)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		3,974,786	3,974,786
Issuance of common stock upon exercise of stock options		$ 24,451			24,451
Vesting of early exercised stock options and restricted common stock		208			208
Vesting of restricted stock units (in shares)			820,002
Stock-based compensation		170,929			170,929
Other comprehensive income (loss)		775				775
Net loss		(189,719)					(189,719)
Ending balance (in shares) at Jul. 31, 2021	[1]		300,584,903
Ending balance at Jul. 31, 2021		$ 4,964,965	$ 30	[1]	$ 6,596,154	$ 1,141	$ (1,632,360)

[1] On March 1, 2021, all shares of the Company’s then-outstanding Class B common stock were automatically converted into the same number of shares of Class A common stock, pursuant to the terms of the Company’s amended and restated certificate of incorporation. No additional shares of Class B common stock will be issued following such conversion. See Note 11 for further details.