CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Statement of Cash Flows [Abstract]
Net income	$ 28,365	$ 7,788
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	15,992	11,574
Stock-based compensation	10,508	2,439
Provision for doubtful accounts	0	319
Deferred income taxes	1,404	92
Accretion of discount on marketable securities	(46)	(135)
Other	(2)	32
Changes in operating assets and liabilities:
Accounts receivable	(8,876)	(23,190)
Prepaid expenses and other current assets	(6,620)	(996)
Accounts payable	16,648	18,289
Accrued expenses	3,195	465
Other liabilities, non-current	(366)	(971)
Net cash provided by operating activities	60,202	15,706
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(22,846)	(12,885)
Capitalized software development costs	(6,755)	(5,638)
Purchases of marketable securities	(53,118)	(22,313)
Proceeds from sales of marketable securities	0	2,295
Proceeds from maturities of marketable securities	25,600	26,750
Net cash used in investing activities	(57,119)	(11,791)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock for employee stock purchase plan	2,635	0
Proceeds from repayments of stockholders’ notes receivable	0	4,268
Proceeds from exercise of stock options	3,327	94
Payments for offering costs	(805)	(1,914)
Payments to acquire treasury stock	(52)	(1)
Net cash provided by financing activities	5,105	2,447
NET INCREASE IN CASH AND CASH EQUIVALENTS	8,188	6,362
CASH AND CASH EQUIVALENTS - Beginning of period	81,188	34,250
CASH AND CASH EQUIVALENTS - End of period	89,376	40,612
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Income taxes paid	4,445	415
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION:
Stock-based compensation capitalized as internal use software costs	628	20
Property and equipment included in accounts payable and accrued expenses	2,712	1,624
Capitalized software costs included in accounts payable and accrued expenses	1,115	636
Deferred offering costs incurred during the period included in accounts payable and accrued expenses	$ 0	$ 22