Your question is Design a messaging platform for scale. 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 messaging platform: how you would tie services together, use websockets, and handle scaling and data issues.
Asked in the System design exam stage. Full stack engineer loop, 2025.
Cover the service boundaries, message lifecycle, WebSocket connection management, persistence, delivery guarantees, horizontal scaling, offline delivery, ordering, retries, and failure handling. Clarify how an ML moderation or message-priority service would integrate without blocking delivery. Explain your assumptions, APIs, data model, observability, and testing strategy.