Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 15,336	$ 8,133
Accumulated depreciation and amortization	(4,484)	(2,841)
Property and equipment, net	10,852	5,292
Capitalized internal-use software
Property, Plant and Equipment [Line Items]
Total property and equipment	6,569	6,167
Computer equipment and servers
Property, Plant and Equipment [Line Items]
Total property and equipment	5,416	631
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment	360	184
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	114	114
Construction in progress
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 2,877	$ 1,037