CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jul. 31, 2018	Jul. 31, 2017
Cash flows from operating activities
Net loss	$ (60,410)	$ (45,769)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,623	1,860
Stock-based compensation	16,586	9,371
Amortization of debt discount and issuance costs	1,094	0
Deferred income taxes	47	62
Change in fair value of warrant liability	0	(101)
Change in operating assets and liabilities:
Accounts receivable	8,029	(1,646)
Prepaid expenses and other current assets	(1,910)	(2,942)
Deferred commissions	(1,320)	(369)
Other long-term assets	46	(634)
Accounts payable	(394)	12
Deferred rent	917	190
Accrued liabilities	1,957	1,245
Deferred revenue	8,834	11,852
Net cash used in operating activities	(24,901)	(26,869)
Cash flows from investing activities
Purchases of property and equipment	(1,561)	(1,626)
Proceeds from maturities of marketable securities	118,000	64,230
Purchases of marketable securities	(300,467)	(68,754)
Net cash used in investing activities	(184,028)	(6,150)
Cash flows from financing activities
Proceeds from exercise of stock options, including early exercised stock options	8,106	5,984
Proceeds from the issuance of common stock under the Employee Stock Purchase Plan	5,626	0
Repurchase of early exercised stock options	(309)	(74)
Proceeds from borrowings on convertible senior notes, net of issuance costs	293,161	0
Payment for purchase of capped calls	(37,086)	0
Proceeds from tenant improvement allowance on build-to-suit lease	376	0
Proceeds from exercise of redeemable convertible preferred stock warrants	0	1
Payment of initial public offering costs	0	(1,177)
Net cash provided by financing activities	269,874	4,734
Effect of exchange rate changes on cash, cash equivalents, and restricted cash	(83)	160
Net increase (decrease) in cash, cash equivalents, and restricted cash	60,862	(28,125)
Cash, cash equivalents, and restricted cash, beginning of period	62,427	69,412
Cash, cash equivalents, and restricted cash, end of period	123,289	41,287
Supplemental cash flow disclosure of noncash investing and financing activities
Vesting of early exercised stock options	835	495
Costs related to initial public offering included in accounts payable and accrued liabilities	0	1,608
Conversion of redeemable convertible preferred stock warrant liability to redeemable convertible preferred stock as a result of warrant exercise	0	1,170
Costs related to issuance of convertible senior notes included in accounts payable and accrued liabilities	2,018	0
Purchases of property and equipment included in accounts payable and accrued liabilities	314	0
Construction in progress related to build-to-suit lease obligations	10,781	0
Reconciliation of cash, cash equivalents, and restricted cash within the condensed consolidated balance sheets, end of period, to the amounts shown in the statements of cash flows above:
Total cash, cash equivalents and restricted cash	$ 62,427	$ 69,412