Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Jul. 31, 2021	Apr. 30, 2021
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 11,030	$ 10,046
Less: Accumulated depreciation	(4,267)	(3,956)
Property and equipment, net	6,763	6,090
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment	246	246
Computer equipment and software
Property, Plant and Equipment [Line Items]
Total property and equipment	1,516	1,461
Capitalized software development costs
Property, Plant and Equipment [Line Items]
Total property and equipment	484	484
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	7,126	6,640
Assets in progress
Property, Plant and Equipment [Line Items]
Total property and equipment	1,627	1,211
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 31	$ 4