Convertible Preferred Stock, Stockholders’ Equity (Deficit) and Equity Incentive Plan - Summary of Stock-based Compensation Expense by Line Item (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 21,795	$ 2,652	$ 46,532	$ 4,627
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	2,369	317	5,101	542
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	3,642	383	7,316	705
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	12,488	1,154	25,554	2,042
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 3,296	$ 798	$ 8,561	$ 1,338