Share-Based Payments - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Jan. 31, 2022	Apr. 30, 2021
Total
Outstanding, beginning balance (in shares)	1,653,646
Granted (in shares)	166,052
Exercised (in shares)	(103,875)
Forfeited (in shares)	(20,500)
Canceled (in shares)	(8,875)
Expired (in shares)	(5,000)
Outstanding, ending balance (in shares)	1,681,448	1,653,646
Vested and expected to vest (in shares)	1,681,448
Exercisable (in shares)	1,292,933
Weighted Average Exercise Price
Outstanding, beginning balance (in usd per share)	$ 3.96
Granted (in usd per share)	9.44
Exercised (in usd per share)	2.24
Forfeited (in usd per share)	7.14
Canceled (in usd per share)	4.83
Expired (in usd per share)	9.60
Outstanding, ending balance (in usd per share)	4.54	$ 3.96
Vested and expected to vest (in usd per share)	4.54
Exercisable (in usd per share)	$ 3.77
Weighted Average Remaining Contractual Life (Years)
Outstanding (in years)	5 years 2 months 19 days	5 years 5 months 1 day
Outstanding, granted (in years)	9 years 7 months 2 days
Vested and expected to vest (in years)	5 years 2 months 19 days
Exercisable (in years)	4 years 3 months 21 days
Aggregate Intrinsic Value
Outstanding	$ 6,611	$ 11,384
Vested and expected to vest	6,611
Exercisable	$ 6,057
Directors and Employees
Total
Outstanding, beginning balance (in shares)	1,618,231
Granted (in shares)	155,552
Exercised (in shares)	(103,875)
Forfeited (in shares)	(20,500)
Canceled (in shares)	(8,875)
Expired (in shares)	0
Outstanding, ending balance (in shares)	1,640,533	1,618,231
Vested and expected to vest (in shares)	1,640,533
Exercisable (in shares)	1,288,349
Non- Employees
Total
Outstanding, beginning balance (in shares)	35,415
Granted (in shares)	10,500
Exercised (in shares)	0
Forfeited (in shares)	0
Canceled (in shares)	0
Expired (in shares)	(5,000)
Outstanding, ending balance (in shares)	40,915	35,415
Vested and expected to vest (in shares)	40,915
Exercisable (in shares)	4,584