CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (unaudited) - USD ($) $ in Thousands	Total	Initial public offering	Convertible Preferred Stock	Convertible Preferred Stock Initial public offering	Common Stock	Common Stock Initial public offering	Additional Paid-in Capital	Additional Paid-in Capital Initial public offering	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Jan. 31, 2018	$ (26,671)				$ 80		$ 6,517		$ (531)	$ (32,737)
Beginning balance (in shares) at Jan. 31, 2018			152,665,804
Beginning balance at Jan. 31, 2018			$ 159,552
Beginning balance (in shares) at Jan. 31, 2018					82,609,638
Issuance of common stock upon exercise of stock options	238				$ 1		237
Issuance of common stock upon exercise of stock options (in shares)					513,140
Stock-based compensation expense	849						849
Other comprehensive income (loss)	(82)								(82)
Net income (loss)	(1,340)									(1,340)
Ending balance at Apr. 30, 2018	(27,006)				$ 81		7,603		(613)	(34,077)
Ending balance (in shares) at Apr. 30, 2018			152,665,804
Ending balance at Apr. 30, 2018			$ 159,552
Ending balance (in shares) at Apr. 30, 2018					83,122,778
Beginning balance at Jan. 31, 2019	$ (7,439)				$ 89		17,760		(135)	(25,153)
Beginning balance (in shares) at Jan. 31, 2019	152,665,804		152,665,804
Beginning balance at Jan. 31, 2019			$ 159,552
Beginning balance (in shares) at Jan. 31, 2019					90,327,435
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)				(152,665,804)
Conversion of convertible preferred stock to common stock upon initial public offering				$ (159,552)
Conversion of convertible preferred stock to common stock upon initial public offering (in shares)						152,665,804
Conversion of convertible promissory notes and accrued interest to common stock upon initial public offering	$ 15,344						15,344
Conversion of convertible promissory notes and accrued interest to common stock upon initial public offering (in shares)					426,223
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 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 exercise of stock options, net of repurchases	$ 1,753				$ 13		1,740
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 (in shares)	13,622,754
Stock-based compensation expense	$ 6,662						6,662
Other comprehensive income (loss)	143								143
Net income (loss)	2,214									2,214
Ending balance at Apr. 30, 2019	$ 719,728				$ 271		$ 742,388		$ 8	$ (22,939)
Ending balance (in shares) at Apr. 30, 2019	0
Ending balance (in shares) at Apr. 30, 2019					272,336,862