Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2017	Jul. 31, 2016
Income Statement [Abstract]
Revenue	$ 40,769	$ 29,556	$ 77,849	$ 56,681
Cost of revenue	10,541	9,067	20,229	17,902
Gross profit	30,228	20,489	57,620	38,779
Operating expenses:
Sales and marketing	30,673	18,132	59,135	34,975
Research and development	6,493	4,673	11,479	9,444
General and administrative	9,569	6,691	18,907	12,674
Total operating expenses	46,735	29,496	89,521	57,093
Loss from operations	(16,507)	(9,007)	(31,901)	(18,314)
Investment income	322	14	322	26
Interest expense	(82)	(30)	(170)	(35)
Other income (expense), net	57	11	(535)	(31)
Loss from operations before income taxes	(16,210)	(9,012)	(32,284)	(18,354)
Provision for income taxes	(189)	0	(221)	(1)
Net loss	$ (16,399)	$ (9,012)	$ (32,505)	$ (18,355)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.18)	$ (0.29)	$ (0.49)	$ (0.59)
Weighted-average number of shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	90,064,644	31,022,319	65,676,665	31,000,444
Other comprehensive income (loss):
Foreign currency translation adjustment	$ 165	$ (474)	$ 357	$ (209)
Unrealized loss on marketable securities	(60)	0	(60)	0
Total comprehensive loss	$ (16,294)	$ (9,486)	$ (32,208)	$ (18,564)