Net Loss Per Share Attributable to Common Stockholders - Potential Shares Excluded From Computation of Diluted Net Loss Per Share (Details) - shares	9 Months Ended
	Jan. 31, 2021	Jan. 31, 2020
Convertible Preferred Stock, 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
Convertible Preferred Stock, 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
Convertible Preferred Stock, 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
Convertible Preferred Stock, 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
Convertible Preferred Stock, 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
Convertible Preferred Stock, 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
Convertible Preferred Stock, 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
Convertible Preferred Stock, 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
Convertible Preferred Stock, 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
Convertible Preferred Stock, 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
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)	41,286,541	33,848,199