Condensed Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue:
Total revenue	$ 70,976	$ 46,985	$ 140,231	$ 93,444
Cost of revenue:
Total cost of revenue	24,926	16,206	51,799	32,060
Gross profit	46,050	30,779	88,432	61,384
Operating expenses:
Marketing	11,715	9,276	23,448	18,910
Operations and technology	34,320	22,997	65,865	44,329
Selling, general and administrative	25,355	14,377	47,674	27,901
Total operating expenses	71,390	46,650	136,987	91,140
Loss from operations	(25,340)	(15,871)	(48,555)	(29,756)
Interest income	610	81	1,015	165
Interest expense	(380)	(526)	(511)	(723)
Other expense, net	(1,706)	(1,279)	(1,987)	(1,387)
Loss before provision for income taxes	(26,816)	(17,595)	(50,038)	(31,701)
Provision for income taxes	59		59
Net loss	(26,875)	(17,595)	(50,097)	(31,701)
Accretion of redeemable convertible preferred stock to redemption value		(1,342)	(3,355)	(2,451)
Net loss attributable to common stockholders	$ (26,875)	$ (18,937)	$ (53,452)	$ (34,152)
Net loss per share attributable to common stockholders, basic and diluted	$ (2.83)	$ (2.28)	$ (5.87)	$ (4.11)
Shares used to compute net loss per share attributable to common stockholders, basic and diluted	9,494,447	8,314,251	9,102,234	8,307,010
Consignment and Service Revenue
Revenue:
Total revenue	$ 60,713	$ 42,178	$ 116,950	$ 83,177
Cost of revenue:
Total cost of revenue	17,200	12,349	33,147	23,926
Direct Revenue
Revenue:
Total revenue	10,263	4,807	23,281	10,267
Cost of revenue:
Total cost of revenue	$ 7,726	$ 3,857	$ 18,652	$ 8,134