X0306 4 2022-01-01 0 0001333835 Casa Systems Inc CASA 0001804155 Slepian Matthew C/O CASA SYSTEMS, INC. 100 OLD RIVER ROAD ANDOVER MA 01810 0 1 0 0 Corporate Controller Common Stock 2022-01-01 4 M 0 5470 A 17122 D Common Stock 2022-01-01 4 F 0 1895 5.67 D 15227 D Restricted Stock Units 2022-01-01 4 M 0 5470 0.00 D Common Stock 5470 16412 D Each Restricted Stock Unit ("RSU") represents the right to receive one share of common stock, $0.001 par value per share (the "Common Stock") of Casa Systems, Inc. (the "Company") upon vesting, subject to the reporting person's continued service relationship with the Company and the other terms and conditions set forth in the applicable RSU agreement. In the sole discretion of the Company's board of directors, the Company may, with respect to any applicable vesting date, deliver to the reporting person Common Stock or cash having a fair market value equal to the number of shares of Common Stock underlying the portion of the RSU that vested on such date, payable within 30 days of the vesting date, less applicable taxes. Shares withheld by the Company to satisfy tax withholding requirements on vesting of RSUs. No shares were sold. These RSUs are scheduled to vest over four years, with 25% of the 21,882 shares underlying the award vesting on January 1, 2022, and 25% of the shares underlying the award vesting at the end of each successive one-year period thereafter. These RSUs have no expiration date. /s/ Timothy C. Rodenberger, as Attorney-in-Fact 2022-01-04