Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Current expense
Federal	$ 0	$ 0	$ 0
State	286	113	2
Foreign	418	267	264
Total	704	380	266
Deferred expense
Federal	0	0	0
State	0	0	0
Foreign	0	0	0
Total	0	0	0
Provision for income taxes	$ 704	$ 380	$ 266

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