CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net loss	$ (18,394)	$ (11,554)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	2,815	2,192
Noncash operating lease cost	689	429
Stock-based compensation expense	3,071	2,255
Change in fair value of convertible preferred stock warrant liability		1,403
Accretion of noncash interest and debt reduction		103
Other	(43)	(2)
Changes in operating assets and liabilities
Accounts receivable	(2,075)	(3,009)
Inventory and other deferred costs	(1,918)	(106)
Prepaid expenses and other current assets	396	(257)
Accounts payable	(348)	(163)
Accrued and other current liabilities	(797)	(624)
Contract liabilities	(7,025)	(1,030)
Operating lease liabilities	(496)	(473)
Other long-term liabilities	128
Net cash used in operating activities	(23,997)	(10,836)
Cash flows from investing activities:
Purchases of available-for-sale debt securities	(67,108)
Proceeds from maturities of available-for-sale debt securities	60,313
Purchases of property and equipment	(855)	(2,801)
Net cash used in investing activities	(7,650)	(2,801)
Cash flows from financing activities:
Proceeds from initial public offering, net of underwriting discounts and commissions		144,025
Payments of costs related to initial public offering		(1,991)
Proceeds from borrowings		20,000
Payments of borrowing costs		(490)
Repayments under borrowing arrangements		(5,000)
Proceeds from exercise of common stock warrants		8
Proceeds from exercise or settlement of equity awards	1,644	611
Net cash provided by financing activities	1,644	157,163
Effect of exchange rates on cash flows and cash equivalents	(1)	(1)
Net change in cash and cash equivalents	(30,004)	143,525
Cash and cash equivalents, beginning of period	55,046	19,744
Cash and cash equivalents, end of period	$ 25,042	$ 163,269