Net Loss Per Share Attributable to Common Stockholders - Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Numerator
Net loss attributable to common stockholders	$ (55,696)	$ (69,378)	$ (33,346)
Class A Common Stock
Denominator
Basic and diluted weighted-average shares outstanding (in shares)	56,677,947	29,133,157	18,662,237
Basic and diluted net loss per share attributable to common stockholders
Basic and diluted net loss per share (in dollars per share)	$ (0.90)	$ (1.94)	$ (1.32)
Class A-1 common stock
Denominator
Basic and diluted weighted-average shares outstanding (in shares)	6,666,665	6,666,665	6,666,665
Basic and diluted net loss per share attributable to common stockholders
Basic and diluted net loss per share (in dollars per share)	$ (0.55)	$ (1.94)	$ (1.32)
Class B Common Stock
Denominator
Basic and diluted weighted-average shares outstanding (in shares)	3,499,992	0	0
Basic and diluted net loss per share attributable to common stockholders
Basic and diluted net loss per share (in dollars per share)	$ (0.35)	$ 0	$ 0