Net Loss Per Share Attributable to Ordinary Shareholders - Schedule of Outstanding Potentially Dilutive Ordinary Shares Excluded from Computation of Diluted Net Loss Per Share Attributable to Ordinary Shareholders (Details) - shares	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	17,864,277	23,716,291	51,601,823
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	15,260,506	22,866,438	22,237,484
RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	2,368,740	595,503	0
Contingently issuable shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	235,031	0	0
Shares subject to repurchase
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	254,350	276,243
Early exercised stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	0	148,630
Redeemable convertible preference shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	0	28,939,466