CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating activities:
Net income (loss)	$ (12,006)	$ (9,356)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization expense	2,185	1,649
Stock-based compensation expense	26,481	10,819
Amortization of premiums and discounts on marketable securities	737	24
Non-cash lease cost	3,420	3,312
Other	17	89
Changes in operating assets and liabilities:
Inventory	(3,703)	(3,264)
Accounts receivable	5,594	5,994
Other current assets	(793)	(633)
Accounts payable	(672)	(52)
Accrued expenses	(361)	747
Operating lease liabilities	(2,410)	(3,110)
Other non-current assets and liabilities, net	0	16
Net cash provided by operating activities	18,489	6,235
Investing activities:
Purchases of investments	(49,375)	(29,049)
Sales and maturities of investments	50,913	39,123
Expenditures for property and equipment	(6,924)	(1,556)
Net cash provided by (used for) investing activities	(5,386)	8,518
Financing activities:
Net proceeds from common stock issuance	9,701	2,182
Payments on employee's behalf for taxes related to vesting of restricted stock units	(1,619)	(163)
Other	(252)	(32)
Net cash provided by financing activities	7,830	1,987
Net increase in cash, cash equivalents, and restricted cash	20,933	16,740
Cash, cash equivalents, and restricted cash at beginning of period	33,831	26,978
Cash, cash equivalents, and restricted cash at end of period	$ 54,764	$ 43,718