Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Apr. 30, 2022	Apr. 30, 2021
Deferred tax assets
Accrued payroll	$ 521	$ 889
Other accruals & reserves	6,185	4,053
Operating lease liability	6,957	1,323
Deferred revenue	442	1,258
Depreciation	2,099	1,588
Net operating losses	114,291	73,189
R&D tax credit	6,618	4,778
Stock based compensation	15,669	3,690
Other	905	327
Gross deferred tax assets	153,687	91,095
Valuation allowance	(144,678)	(88,015)
Total deferred tax assets	9,009	3,080
Deferred tax liabilities
Prepaid expenses	(2,384)	(1,883)
Operating lease right-of-use assets	(6,625)	(1,197)
Total deferred tax liabilities	(9,009)	(3,080)
Net deferred tax assets (liabilities)	$ 0	$ 0