CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' (DEFICIT) EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive (Loss) Income	(Accumulated Deficit) Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding (in shares)		79,650,896
Beginning balance (in shares) at Jan. 31, 2017	154,031,604
Beginning balance at Jan. 31, 2017	$ 159,757
Increase (Decrease) in Temporary Equity [Roll Forward]
Repurchase of Series A convertible preferred stock (in shares)	(1,365,800)
Repurchase of Series A convertible preferred stock	$ (205)
Ending balance (in shares) at Jan. 31, 2018	152,665,804
Ending balance at Jan. 31, 2018	$ 159,552
Beginning balance at Jan. 31, 2017	(28,838)	$ 77	$ 0	$ 0	$ (28,915)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of Series A convertible preferred stock	(4,405)		(4,405)
Issuance of common stock upon exercise of stock options (in shares)		2,958,742
Issuance of common stock upon exercise of stock options	596	$ 3	593
Stock-based compensation expense	10,329		10,329
Other comprehensive income (loss)	(531)			(531)
Net income (loss)	(3,822)				(3,822)
Ending balance at Jan. 31, 2018	$ (26,671)	$ 80	6,517	(531)	(32,737)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding (in shares)		82,609,638
Ending balance (in shares) at Jan. 31, 2019	152,665,804
Ending balance at Jan. 31, 2019	$ 159,552
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		7,717,797
Issuance of common stock upon exercise of stock options	2,311	$ 9	2,302
Stock-based compensation expense	8,941		8,941
Other comprehensive income (loss)	396			396
Net income (loss)	7,584				7,584
Ending balance at Jan. 31, 2019	(7,439)	$ 89	17,760	(135)	(25,153)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding (in shares)		90,327,435
Conversion of convertible preferred stock to common stock upon initial public offering	$ (159,552)
Ending balance (in shares) at Jan. 31, 2020	0
Ending balance at Jan. 31, 2020	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)	19,003,652
Conversion of convertible preferred stock to common stock upon initial public offering (in shares)		152,665,804
Conversion of convertible preferred stock to common stock upon initial public offering	$ 159,552	$ 153	159,399
Conversion of convertible preferred stock to common stock upon initial public offering (in shares)		426,223
Conversion of convertible preferred stock to common stock upon initial public offering	15,344		15,344
Issuance of common stock upon initial public offering and private placement net of underwriting discounts and commissions and other offering costs (in shares)		15,819,646
Issuance of common stock upon initial public offering and private placement, net of underwriting discounts and commissions and other offering costs	541,499	$ 16	541,483
Issuance of common stock upon exercise of stock options, net of repurchases (in shares)		18,501,767
Issuance of common stock upon exercise of stock options, net of repurchases and release of restricted stock units	9,771	$ 19	9,752
Issuance of common stock reserved for charitable donation (in shares)		500,000
Issuance of common stock reserved for charitable donations	0
Proceeds from issuance of common stock fro employee stock purchase plan (in shares)		490,268
Issuance of common stock for employee stock purchase plan	15,482		15,482
Stock-based compensation expense	73,485		73,485
Other comprehensive income (loss)	944			944
Net income (loss)	25,305				25,305
Ending balance at Jan. 31, 2020	$ 833,943	$ 277	$ 832,705	$ 809	$ 152
Increase (Decrease) in Temporary Equity [Roll Forward]
Conversion of convertible preferred stock to common stock upon initial public offering (in shares)	(152,665,804)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding (in shares)		278,731,143