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Income Taxes - Reconciliation of Statutory Rate and Effective Tax Rate (Details)
12 Months Ended
Apr. 30, 2022
Apr. 30, 2021
Apr. 30, 2020
Income Tax Disclosure [Abstract]      
Statutory federal tax expense rate 21.00% 21.00% 21.00%
State tax, net of federal benefit 1.00% 0.00% 8.00%
Research tax credits 4.00% 3.00% (34.00%)
Stock compensation 7.00% 0.00% 0.00%
Other permanent adjustment 0.00% 1.00% 1.00%
Other 1.00% 0.00% (2.00%)
Foreign rate differential (26.00%) (25.00%) 25.00%
Change in valuation allowance (4.00%) (8.00%) 0.00%
Withholding Taxes (4.00%) (2.00%) 21.00%
Foreign tax credit 0.00% 0.00% (4.00%)
Effective tax rate 0.00% (10.00%) 36.00%