WebSocket load balancing
Design load balancing for a real-time presence/WebSocket service where each user holds a long-lived connection and is pinned to one server that owns their session state. You run thousands of servers, need even connection distribution, and must minimize how many users get disconnected when you add/remove servers during a deploy or autoscale event. Explain the routing scheme and how you handle a server dying mid-session.
What a strong answer looks like
Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts (data model, bottlenecks, consistency, failure modes) and name the trade-offs you are making.
Clarify5:00 left
Estimate5:00 planned
Design15:00 planned
Deep dive12:00 planned
Failure8:00 planned
Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.
Run or narrate your approach, then ask the coach.