Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Redeemable convertible preferred stock, beginning balance (in shares) at Jan. 31, 2019	41,273,345
Redeemable convertible preferred stock, beginning balance at Jan. 31, 2019	$ 173,023
Increase (Decrease) in Temporary Equity [Roll Forward]
Conversion of convertible preferred stock to common stock in connection with initial public offering (in shares)	(41,273,345)
Conversion of convertible preferred stock to common stock in connection with initial public offering	$ (173,023)
Redeemable convertible preferred stock, ending balance (in shares) at Jul. 31, 2019	0
Redeemable convertible preferred stock, ending balance at Jul. 31, 2019	$ 0
Beginning balance (in shares) at Jan. 31, 2019		23,189,921
Beginning balance at Jan. 31, 2019	(68,930)	$ 0	$ 59,938		$ (128,868)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options and restricted stock agreements, net of repurchases (in shares)		1,165,345
Issuance of common stock upon exercise of stock options and restricted stock agreements, net of repurchases	2,785		2,785
Vesting of restricted stock units, net of employee payroll taxes (in shares)		183
Vesting of restricted stock units, net of employee payroll taxes	(10)		(10)
Exercise of common stock warrants (in shares)		737,807
Repayment of promissory note	515		515
Issuance of common stock in connection with initial public offering, net of underwriting discounts and issuance costs (in shares)		9,860,500
Issuance of common stock in connection with initial public offering, net of underwriting discounts and issuance costs	213,697		213,697
Conversion of convertible preferred stock to common stock in connection with initial public offering (in shares)		41,273,345
Conversion of convertible preferred stock to common stock in connection with initial public offering	173,023		173,023
Vesting of early exercised options	672		672
Stock-based compensation	12,045		12,045
Net loss	(24,634)				(24,634)
Ending balance (in shares) at Jul. 31, 2019		76,227,101
Ending balance at Jul. 31, 2019	$ 309,163	$ 0	462,665		(153,502)
Redeemable convertible preferred stock, ending balance (in shares) at Jul. 31, 2019	0
Redeemable convertible preferred stock, ending balance at Jul. 31, 2019	$ 0
Beginning balance (in shares) at Apr. 30, 2019		76,013,403
Beginning balance at Apr. 30, 2019	313,627	$ 0	454,559		(140,932)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options and restricted stock agreements, net of repurchases (in shares)		213,515
Issuance of common stock upon exercise of stock options and restricted stock agreements, net of repurchases	545		545
Vesting of restricted stock units, net of employee payroll taxes (in shares)		183
Vesting of restricted stock units, net of employee payroll taxes	(10)		(10)
Vesting of early exercised options	338		338
Stock-based compensation	7,233		7,233
Net loss	(12,570)				(12,570)
Ending balance (in shares) at Jul. 31, 2019		76,227,101
Ending balance at Jul. 31, 2019	309,163	$ 0	462,665		(153,502)
Beginning balance (in shares) at Jan. 31, 2020		77,793,540
Beginning balance at Jan. 31, 2020	307,938	$ 0	487,008	$ 137	(179,207)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options and restricted stock agreements, net of repurchases (in shares)		1,286,892
Issuance of common stock upon exercise of stock options and restricted stock agreements, net of repurchases	5,771		5,771
Vesting of restricted stock units, net of employee payroll taxes (in shares)		93,942
Vesting of restricted stock units, net of employee payroll taxes	(1,743)		(1,743)
Vesting of early exercised options	507		507
Equity component of convertible senior notes, net of issuance costs	68,478		68,478
Purchases of capped calls related to convertible senior notes	(35,708)		(35,708)
Issuance of common stock in connection with employee stock purchase plan (in shares)		181,253
Issuance of common stock in connection with employee stock purchase plan	3,558		3,558
Other comprehensive income	919			919
Stock-based compensation	18,298		18,298
Net loss	(26,147)				(26,147)
Ending balance (in shares) at Jul. 31, 2020		79,355,627
Ending balance at Jul. 31, 2020	341,871	$ 0	546,169	1,056	(205,354)
Beginning balance (in shares) at Apr. 30, 2020		78,526,004
Beginning balance at Apr. 30, 2020	307,543	$ 0	497,430	779	(190,666)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options and restricted stock agreements, net of repurchases (in shares)		557,467
Issuance of common stock upon exercise of stock options and restricted stock agreements, net of repurchases	3,927		3,927
Vesting of restricted stock units, net of employee payroll taxes (in shares)		90,903
Vesting of restricted stock units, net of employee payroll taxes	(1,697)		(1,697)
Vesting of early exercised options	191		191
Equity component of convertible senior notes, net of issuance costs	68,478		68,478
Purchases of capped calls related to convertible senior notes	(35,708)		(35,708)
Issuance of common stock in connection with employee stock purchase plan (in shares)		181,253
Issuance of common stock in connection with employee stock purchase plan	3,558		3,558
Other comprehensive income	277			277
Stock-based compensation	9,990		9,990
Net loss	(14,688)				(14,688)
Ending balance (in shares) at Jul. 31, 2020		79,355,627
Ending balance at Jul. 31, 2020	$ 341,871	$ 0	$ 546,169	$ 1,056	$ (205,354)