Stock-Based Compensation - Schedule of Stock Option Activity (Details) - 2021 Plan and 2017 Plan $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares
Stock Based Compensation Details [Line Items]
Options opening balance | shares	17,167,165
Options Granted | shares	9,681,736
Options Exercised | shares	(472,256)
Options Forfeited | shares	(347,858)
Options ending balance | shares	26,028,787	17,167,165
Options, Vested and expected to vest | shares	26,028,787
Options, Exercisable | shares	18,845,930
Weighted average exercise price, beginning balance | $ / shares	$ 1.63
Weighted average exercise price, Granted | $ / shares	8.57
Weighted average exercise price, Exercised | $ / shares	0.37
Weighted average exercise price, Forfeited | $ / shares	6.01
Weighted average exercise price, ending balance | $ / shares	4.17	$ 1.63
Weighted average exercise price, Vested and expected to vest | $ / shares	4.17
Weighted average exercise price, Exercisable | $ / shares	$ 3.47
Weighted average contract life	7 years 8 months 12 days	7 years 3 months 18 days
Weighted average contract life, Vested and expected to vest	7 years 8 months 12 days
Weighted average contract life, Exercisable	7 years 1 month 6 days
Aggregate Intrinsic Value ending balance | $	$ 96,869	$ 100,633
Aggregate Intrinsic Value, Vested and expected to vest | $	96,869
Aggregate Intrinsic Value, Exercisable | $	$ 82,250