Revenue, Deferred Revenue and Remaining Performance Obligations - Revenue from contracts type of customer and Region based on shipping address of customers (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2019	Jul. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 108,108	$ 55,701	$ 204,185	$ 102,990
Percentage of revenue	100.00%	100.00%	100.00%	100.00%
United States
Disaggregation of Revenue [Line Items]
Total revenue	$ 80,146	$ 44,338	$ 152,454	$ 80,293
Percentage of revenue	74.00%	80.00%	75.00%	78.00%
Europe, Middle East, and Africa
Disaggregation of Revenue [Line Items]
Total revenue	$ 15,006	$ 5,108	$ 28,419	$ 11,017
Percentage of revenue	14.00%	9.00%	14.00%	11.00%
Asia Pacific
Disaggregation of Revenue [Line Items]
Total revenue	$ 8,613	$ 4,000	$ 14,843	$ 7,662
Percentage of revenue	8.00%	7.00%	7.00%	7.00%
Other
Disaggregation of Revenue [Line Items]
Total revenue	$ 4,343	$ 2,255	$ 8,469	$ 4,018
Percentage of revenue	4.00%	4.00%	4.00%	4.00%
Channel partners
Disaggregation of Revenue [Line Items]
Total revenue	$ 70,438	$ 36,936	$ 134,897	$ 70,094
Percentage of revenue	65.00%	66.00%	66.00%	68.00%
Direct customers
Disaggregation of Revenue [Line Items]
Total revenue	$ 37,670	$ 18,765	$ 69,288	$ 32,896
Percentage of revenue	35.00%	34.00%	34.00%	32.00%