Start by clarifying requirements and constraints, then design a basic load balancer with a simple assignment strategy like round-robin or least connections. Iteratively extend the design to handle disconnections, object-level stickiness, per-server capacity limits, and graceful shutdown, discussing trade-offs at each step. Emphasize scalability, fault tolerance, and consistency.
Pro tip: Demonstrate awareness of real-world constraints by discussing how to handle sticky sessions without overloading servers, and how to ensure zero-downtime during server shutdowns. Mention monitoring and metrics for capacity planning.
Ask questions to understand scale, expected number of connections, server capacity, and stickiness requirements. Define what 'object-level stickiness' means (e.g., same user or notebook session routed to same server).
Propose a simple assignment strategy such as round-robin or least connections. Discuss how the load balancer tracks server states and assigns new WebSocket connections.
Explain how to detect disconnections (heartbeats, timeouts) and update server load. For reconnections, decide whether to reassign or attempt to route back to the same server based on stickiness.
Introduce a mapping (e.g., consistent hashing or a lookup table) to route connections for the same object (user, notebook) to the same server. Enforce per-server capacity limits by rejecting or queuing connections when full.
Describe a process for draining connections from a server being shut down: stop accepting new connections, notify clients to reconnect, and re-route existing connections to other servers without data loss.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.