Net Loss Per Share Attributable to Common Stockholders - Potential Shares Excluded From Computation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Series A*
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially antidilutive shares excluded from computation of net loss per share (in shares)	0	3,499,992	3,499,992
Series B*
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially antidilutive shares excluded from computation of net loss per share (in shares)	0	4,559,999	4,559,999
Series B-1A*
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially antidilutive shares excluded from computation of net loss per share (in shares)	0	2,430,635	2,430,635
Series B-1B*
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially antidilutive shares excluded from computation of net loss per share (in shares)	0	92,769	92,769
Series C*
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially antidilutive shares excluded from computation of net loss per share (in shares)	0	2,779,738	2,779,738
Series D
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially antidilutive shares excluded from computation of net loss per share (in shares)	0	12,278,422	12,278,422
Series E
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially antidilutive shares excluded from computation of net loss per share (in shares)	0	540,003	540,003
Series F
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially antidilutive shares excluded from computation of net loss per share (in shares)	0	5,399,581	5,399,581
Series G
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially antidilutive shares excluded from computation of net loss per share (in shares)	0	3,893,701	2,610,376
Series H
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially antidilutive shares excluded from computation of net loss per share (in shares)	0	1,653,928	0
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially antidilutive shares excluded from computation of net loss per share (in shares)	39,577,809	33,533,380	23,821,538
RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially antidilutive shares excluded from computation of net loss per share (in shares)	447,095	0	0