This is the Q&A from "Troubleshooting ASA Firewalls - Understanding Firewall Architecture, Troubleshooting CPU Issues, Understanding Fail over and CSC-SSM vs ASA-NGFW (CX)"
Q. How does data flow through the ASA when we use an ASA-SSM module?
A. An ASA-SSM could either be the 4-port expansion module or the CSC or AIP SSM module. If it is the 4-port SSM module, then that will still be processed by the ASA's CPU but the CPU uplink is restricted to 1Gbps. Traffic destined to the AIP or CSC module will be redirected by the ASA over the backplane to the module and returned back to the ASA by the module if allowed.