Stock-based compensation - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		12 Months Ended
		Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Number of Shares Underlying Outstanding Options
Number of shares underlying outstanding options, options exercised (in shares)	[1]		(423)
2015 Stock Plan
Number of Shares Available for Grant
Number of shares available for grant, beginning balance (in shares)		1,587,195
Number of shares available for grant, options repurchased (in shares)		220,561
Number of shares available for grant, options exercised (in shares)			0
Number of shares available for grant, options cancelled (in shares)		378,639
Number of shares available for grant, ending balance (in shares)		2,186,395		1,587,195
Number of Shares Underlying Outstanding Options
Number of shares underlying outstanding options, beginning balance (in shares)		25,732,503
Number of shares underlying outstanding options, options repurchased (in shares)			0
Number of shares underlying outstanding options, options exercised (in shares)		(727,114)
Number of shares underlying outstanding options, options cancelled (in shares)		(378,641)
Number of shares underlying outstanding options, ending balance (in shares)		24,626,748		25,732,503
Number of shares underlying outstanding options, vested and expected to vest (in shares)		24,626,748
Number of shares underlying outstanding options, exercisable (in shares)		5,969,870
Weighted- Average Exercise Price per Share
Weighted average exercise price, beginning balance (in dollars per share)		$ 0.39
Weighted average exercise price, options repurchased (in dollars per share)		0.14
Weighted average exercise price, options exercised (in dollars per share)		0.13
Weighted average exercise price, options cancelled (in dollars per share)		0.15
Weighted average exercise price, ending balance (in dollars per share)		0.41		$ 0.39
Weighted average exercise price, options vested and expected to vest (in dollars per share)		0.41
Weighted average exercise price, options exercisable (in dollars per share)		$ 0.26
Weighted- Average Remaining Contractual Term (in years)
Stock options outstanding, weighted average remaining contractual term		9 years 4 months 24 days		9 years 7 months 6 days
Stock options exercised, weighted average remaining contractual term		9 years
Stock options vested and expected to vest, weighted average remaining contractual term		9 years 4 months 24 days
Stock options exercisable, weighted average remaining contractual term		9 years 2 months 12 days
Aggregate Intrinsic Value
Stock options outstanding, aggregate intrinsic value, beginning balance		$ 245,746
Stock options exercised, aggregate intrinsic value		6,083
Stock options outstanding, aggregate intrinsic value, ending balance		199,328		$ 245,746
Stock options vested and expected to vest, aggregate intrinsic value		199,328
Stock options exercisable, aggregate intrinsic value		$ 49,206

[1] The shares of the Company’s common and redeemable convertible preferred stock, prior to the Merger (as defined in Note 1), have been retroactively restated as shares reflecting the exchange ratio of approximately 0.703 established in the Merger as described in Note 1.