Share-Based Payments - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Oct. 31, 2021	Oct. 31, 2021	Apr. 30, 2021
Total
Outstanding, beginning balance (in shares)		1,653,646
Granted (in shares)	0	85,532
Exercised (in shares)		(82,078)
Forfeited (in shares)		(12,500)
Canceled (in shares)		(4,672)
Expired (in shares)		(5,000)
Outstanding, ending balance (in shares)	1,634,928	1,634,928	1,653,646
Vested and expected to vest (in shares)	1,634,928	1,634,928
Exercisable (in shares)	1,300,678	1,300,678
Weighted Average Exercise Price
Outstanding, beginning balance (in usd per share)		$ 3.96
Granted (in usd per share)		9.01
Exercised (in usd per share)		1.91
Forfeited (in usd per share)		6.74
Canceled (in usd per share)		3.36
Expired (in usd per share)		9.60
Outstanding, ending balance (in usd per share)	$ 4.29	4.29	$ 3.96
Vested and expected to vest (in usd per share)	4.29	4.29
Exercisable (in usd per share)	$ 3.69	$ 3.69
Weighted Average Remaining Contractual Life (Years)
Outstanding (in years)		5 years 3 months 7 days	5 years 5 months 1 day
Outstanding, granted (in years)		9 years 7 months 24 days
Vested and expected to vest (in years)		5 years 3 months 7 days
Exercisable (in years)		4 years 6 months 3 days
Aggregate Intrinsic Value
Outstanding	$ 9,246	$ 9,246	$ 11,384
Vested and expected to vest	9,246	9,246
Exercisable	$ 8,189	$ 8,189
Directors and Employees
Total
Outstanding, beginning balance (in shares)		1,618,231
Granted (in shares)		82,532
Exercised (in shares)		(82,078)
Forfeited (in shares)		(12,500)
Canceled (in shares)		(4,672)
Expired (in shares)		0
Outstanding, ending balance (in shares)	1,601,513	1,601,513	1,618,231
Vested and expected to vest (in shares)	1,601,513	1,601,513
Exercisable (in shares)	1,296,094	1,296,094
Non- Employees
Total
Outstanding, beginning balance (in shares)		35,415
Granted (in shares)		3,000
Exercised (in shares)		0
Forfeited (in shares)		0
Canceled (in shares)		0
Expired (in shares)		(5,000)
Outstanding, ending balance (in shares)	33,415	33,415	35,415
Vested and expected to vest (in shares)	33,415	33,415
Exercisable (in shares)	4,584	4,584