Your question is Chat Application Architecture. 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 chat application (e.g., WeChat). Asked in the Virtual Onsite - Round 5 stage. High level system design round. Clarify the product scope, scale, reliability, consistency, privacy, and latency requirements before proposing an architecture. Explain how ML components such as abuse detection, spam filtering, smart replies, or message retrieval would fit into the system, including offline training, online inference, evaluation, and failure handling.