CONSOLIDATED STATEMENTS OF CASH FLOW - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Cash flows from operating activities:
Net income (loss)	$ 25,305	$ 7,584	$ (3,822)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Stock-based compensation expense	73,109	8,941	10,329
Amortization of deferred contract acquisition costs	37,101	20,839	9,023
Depreciation and amortization	16,449	7,008	2,786
Non-cash operating lease cost	6,885	0	0
Provision for accounts receivable allowances	6,370	1,953	727
Other	(1,068)	37	95
Changes in operating assets and liabilities:
Accounts receivable	(64,715)	(41,040)	(16,560)
Prepaid expenses and other assets	(24,805)	(7,971)	(3,443)
Deferred contract acquisition costs	(72,714)	(45,769)	(27,470)
Accounts payable	(2,030)	832	1,254
Accrued expenses and other liabilities	51,179	27,407	15,011
Deferred revenue	106,286	71,511	31,496
Operating lease liabilities, net	(5,460)	0	0
Net cash provided by operating activities	151,892	51,332	19,426
Cash flows from investing activities:
Purchases of marketable securities	(800,228)	(78,016)	(143,329)
Maturities of marketable securities	343,554	68,747	39,710
Purchases of property and equipment	(38,084)	(28,432)	(9,738)
Purchase of equity investment	(3,000)	0	0
Loans to employees	(1,569)	0	0
Purchases of intangible assets	(141)	(2,018)	0
Net cash used in investing activities	(499,468)	(39,719)	(113,357)
Cash flows from financing activities:
Proceeds from initial public offering and private placement, net of underwriting discounts and commissions and other offering costs	542,492	(939)	0
Proceeds from international employee stock sales to be remitted to employees and tax authorities	48,547	0	0
Proceeds from issuance of common stock for employee stock purchase plan	15,482	0	0
Proceeds from exercise of stock options, net of repurchases	9,169	3,565	733
Proceeds from issuance of convertible promissory notes and derivatives	0	15,000	0
Principal payments on capital lease obligations	0
Principal payments on capital lease obligations		(92)	(120)
Repurchase of convertible preferred stock	0	0	(4,610)
Net cash provided by (used in) financing activities	615,690	17,534	(3,997)
Net increase (decrease) in cash, cash equivalents, and restricted cash	268,114	29,147	(97,928)
Cash, cash equivalents, and restricted cash—beginning of period	65,968	36,821	134,749
Cash, cash equivalents, and restricted cash—end of period	334,082	65,968	36,821
Supplemental disclosures of cash flow information
Cash paid for income taxes	1,070	214	133
Supplemental disclosures of non-cash investing and financing information
Purchase of equipment during the period included in accounts payable and accrued expenses	1,422	3,284	392
Purchase of property and equipment under capital lease	0	0	212
Vesting of early exercised stock options and restricted stock awards	725	277	175
Deferred offering costs, accrued but not paid	0	1,490	0
Reconciliation of cash, cash equivalents, and restricted cash within the consolidated balance sheets to the amounts shown in the consolidated statements of cash flows above:
Cash and cash equivalents	283,134	63,624	36,146
Total cash, cash equivalents, and restricted cash	334,082	36,821	36,821
Class B Common Stock
Cash flows from operating activities:
Net income (loss)	19,855	7,584	(3,822)
Supplemental disclosures of non-cash investing and financing information
Conversion of convertible preferred stock to Class B common stock upon initial public offering	159,552	0	0
Class A Common Stock
Cash flows from operating activities:
Net income (loss)	5,450	0	0
Supplemental disclosures of non-cash investing and financing information
Conversion of debt to Class A common stock	$ 15,344	$ 0	$ 0