Balance Sheet Details - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020	Apr. 30, 2020
Balance Sheet Details [Line Items]
Depreciation expense	$ 1,000	$ 200	$ 3,000	$ 600
Common stock exercised prior to vesting, included in accrued and other current liabilities	6,100		6,100		$ 2,200
Transfers to stockholders' deficit, included in accrued and other current liabilities	6,589	$ 2,061	14,270	$ 5,424
Lease liability, current portion	3,800		3,800		3,500
General expenses, included in accrued and other current	$ 3,100		3,100		1,500
Options Exercised in Advance of Vesting
Balance Sheet Details [Line Items]
Transfers to stockholders' deficit, included in accrued and other current liabilities			$ 2,100		$ 700