CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jan. 31, 2021	Apr. 30, 2020
CURRENT ASSETS:
Cash and cash equivalents	$ 70,894	$ 36,262
Accounts receivable	27,113	8,606
Contract assets	5,545	3,300
Inventory	11,946	10,883
Prepaid expenses	813	712
Total current assets	116,311	59,763
Property and equipment, net	32,162	27,105
Operating lease right-of-use assets	19,053	20,100
Restricted cash	350	350
Other assets	302	302
Total assets	168,178	107,620
CURRENT LIABILITIES:
Accounts payable	6,855	5,926
Accrued payroll and related costs	6,500	3,019
Contract liabilities	47,707	29,120
Current portion of operating lease liabilities	1,334	1,228
Note payable	0	4,379
Other current liabilities	179	808
Total current liabilities	62,575	44,480
Operating lease liabilities, less current portion	20,233	21,244
Total liabilities	82,808	65,724
Commitments and contingencies (Note 8)
STOCKHOLDERS' EQUITY:
Preferred stock, $0.001 par value; 5,000 shares authorized; 1,648 shares issued and outstanding at January 31, 2021 and April 30, 2020, respectively	2	2
Common stock, $0.001 par value; 150,000 shares authorized; 60,827 and 56,483 shares issued and outstanding at January 31, 2021 and April 30, 2020, respectively	61	56
Additional paid-in-capital	647,157	612,909
Accumulated deficit	(561,850)	(571,071)
Total stockholders' equity	85,370	41,896
Total liabilities and stockholders' equity	$ 168,178	$ 107,620