CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (in shares) at Jan. 31, 2019		152,665,804	90,327,435
Beginning balance at Jan. 31, 2019	$ (7,439)	$ 159,552	$ 89	$ 17,760	$ (135)	$ (25,153)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of convertible preferred stock to common stock upon initial public offering (in shares)		(152,665,804)	152,665,804
Conversion of convertible preferred stock to common stock upon initial public offering	159,552	$ (159,552)	$ 153	159,399
Conversion of convertible promissory notes and accrued interest to common stock upon initial public offering (in shares)			426,223
Conversion of convertible promissory notes and accrued interest 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)			13,097,754
Issuance of common stock upon exercise of stock options, net of repurchases	1,753		$ 13	1,740
Stock-based compensation expense	6,662			6,662
Other comprehensive income	143				143
Net income (loss)	2,214					2,214
Ending balance (in shares) at Apr. 30, 2019		0	272,336,862
Ending balance at Apr. 30, 2019	719,728	$ 0	$ 271	742,388	8	(22,939)
Beginning balance (in shares) at Jan. 31, 2020		0	278,731,143
Beginning balance at Jan. 31, 2020	$ 833,943	$ 0	$ 277	832,705	809	152
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)	3,232,991		3,232,991
Issuance of common stock upon exercise of stock options	$ 9,725		$ 3	9,722
Issuance of restricted shares of common stock, net (in shares)			27,877
Issuance of restricted shares of common stock	0
Charitable donation of common stock	1,000			1,000
Stock-based compensation expense	28,810			28,810
Other comprehensive income	1,078				1,078
Net income (loss)	27,075					27,075
Ending balance (in shares) at Apr. 30, 2020		0	281,992,011
Ending balance at Apr. 30, 2020	$ 901,631	$ 0	$ 280	$ 872,237	$ 1,887	$ 27,227