Start by clarifying requirements (scale, latency, notification types) and then propose a high-level architecture that covers real-time delivery, reliability, and scalability. Focus on frontend-relevant aspects like WebSocket management, state synchronization, and user experience, while discussing trade-offs between different technologies.
Pro tip: Emphasize how you would handle reconnection and missed notifications to ensure a seamless user experience, as this demonstrates deep understanding of real-world frontend challenges.
Ask about scale (number of users, notifications per second), latency expectations, notification types (e.g., friend requests, game updates), and delivery guarantees (at-least-once, exactly-once).
Outline components: clients, WebSocket gateway, notification service, message queue, and database. Explain how notifications flow from producers to consumers.
Choose WebSockets for bidirectional communication, with fallbacks like SSE or long-polling. Discuss connection management, heartbeats, and scaling WebSocket servers.
Describe how to handle disconnections, missed notifications (e.g., using sequence IDs and fetching missed messages), and offline storage (IndexedDB, Service Workers).
Discuss trade-offs between push vs. pull, message ordering, deduplication, batching, and how to optimize for performance and battery life on mobile.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.