Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jul. 31, 2018	Jul. 31, 2017
Operating activities:
Net loss	$ (39,232)	$ (32,505)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,241	2,385
Provision for bad debts	353	169
Stock-based compensation expense	19,021	9,065
Change in fair value of convertible preferred stock warrant liability	0	491
Deferred income taxes	(57)	6
Amortization of deferred financing costs	66	69
Amortization of premium on marketable securities	47	44
Changes in operating assets and liabilities:
Accounts receivable	16,065	13,168
Prepaid expenses and other current assets	(3,690)	(2,571)
Deferred commissions	(1,581)	(487)
Other long term assets	(94)	(119)
Accounts payable, accrued expenses and other current liabilities	4,875	(3,506)
Deferred revenue	(1,434)	125
Deferred rent	(598)	(303)
Other long term liabilities	2	20
Net cash used in operating activities	(3,016)	(13,949)
Investing activities:
Purchases of marketable securities	(24,692)	(94,446)
Maturities of marketable securities	31,067	0
Capital expenditures	(2,703)	(1,886)
Net cash provided by (used in) investing activities	3,672	(96,332)
Financing activities:
Proceeds from initial public offering, net of underwriting discounts and commissions	0	123,527
Payments of deferred offering costs	0	(4,263)
Proceeds from exercise of stock options	10,165	2,381
Proceeds from exercise of warrants	0	79
Repayments on Revolving Line	0	(5,000)
Payments of deferred financing costs	(159)	(99)
Proceeds, net from employee stock purchase plan withholdings	2,479	1,337
Net cash provided by financing activities	12,485	117,962
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(353)	278
Net increase in cash, cash equivalents and restricted cash	12,788	7,959
Cash, cash equivalents and restricted cash at beginning of period	34,367	24,920
Cash, cash equivalents and restricted cash at end of period	47,155	32,879
Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents	47,155	32,879
Restricted cash	0	0
Cash, cash equivalents and restricted cash at end of period	$ 47,155	$ 32,879