Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating activities
Net loss	$ (11,610)	$ (9,405)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	1,046	409
Inventory step-up amortization	438
Stock-based compensation expense	2,109	1,284
Non-cash interest expense	22	24
Loss on disposal of fixed assets	69
Changes in operating assets and liabilities:
Accounts receivable	(1,174)	(465)
Prepaid expenses and other assets	(495)	142
Inventory	(1,398)	(1,798)
Other non-current assets	32	3
Accounts payable	(1,145)	(1,321)
Accrued compensation and benefits, other accrued expenses and other current liabilities	(1,710)	(327)
Contract acquisition costs	(110)	(25)
Operating lease liabilities	253
Other non-current liabilities	(177)	6,082
Deferred revenue	671	45
Net cash used in operating activities	(13,179)	(5,352)
Investing activities
Purchases of property and equipment	(426)	(5,917)
Net cash used in investing activities	(426)	(5,917)
Financing activities
Proceeds from stock options exercised	496	503
Proceeds from ESPP purchase	440	328
Payments on notes payable	(75)
Net cash provided by financing activities	861	831
Net decrease in cash and cash equivalents	(12,744)	(10,438)
Effect of foreign currency exchange rate on cash	(78)
Cash, restricted cash, and cash equivalents at beginning of period	110,181	45,429
Cash, restricted cash, and cash equivalents at end of period	97,359	34,991
Supplemental cash flow information
Cash paid for interest	155	160
Purchases of property and equipment included in accounts payable	102	11
Reconciliation of cash, cash equivalents, and restricted cash:
Total cash, cash equivalents, and restricted cash	$ 97,359	$ 34,991