X0407 4 2023-05-18 0 0001333835 Casa Systems Inc CASA 0001032663 STYSLINGER WILLIAM C III C/O CASA SYSTEMS, INC. 100 OLD RIVER ROAD ANDOVER MA 01810 1 0 0 0 0 Common Stock 2023-05-18 4 M 0 40285 A 710464 D Restricted Stock Units 2023-05-18 4 M 0 40285 0.00 D Common Stock 40285 0 D Restricted stock unites ("RSUs") converted into common stock, $0.001 par value per share (the "Common Stock"), of Casa Systems, Inc. (the "Company") on a one-for-one basis upon vesting of the RSU. Each RSU represents the right to receive one share of Common Stock of 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. The RSUs vested as to 100% of the original number of shares underlying the RSU Award on May 18, 2023. The RSUs have no expiration date. /s/ Timothy C. Rodenberger, as Attorney-in-Fact 2023-05-22