Your question is Group Chat API and DB Schema. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
Design a group chat application: provide the needed APIs, DB schema, and a high-level diagram of services.
Asked in the system design stage. Explain your assumptions, define the core entities and request flows, and show how messages are sent, stored, retrieved, and delivered to group members.