This is one of those questions where you think you know it until you're actually drawing it out.
Start by clarifying requirements (e.g., real-time collaboration, offline support, scale) and then outline a high-level architecture covering data model, conflict resolution, and infrastructure. Focus on trade-offs between consistency, latency, and complexity, and tie choices back to Vercel's edge-first, serverless strengths.
Pro tip: Emphasize operational simplicity and real-time performance by leveraging CRDTs with edge functions, and mention how you'd handle offline edits and conflict resolution without over-engineering. Show awareness of Vercel's primitives like Edge Config and KV for low-latency sync.
Ask about expected scale (concurrent editors, document size), real-time vs. async collaboration, offline support, and security/compliance needs. This narrows design choices and shows you prioritize user needs.
Choose a document representation (e.g., rich text as a tree or sequence) and a conflict resolution strategy: OT (Operational Transformation) or CRDTs (Conflict-free Replicated Data Types). Discuss trade-offs: OT is simpler for text but requires central server; CRDTs enable peer-to-peer and offline but have higher metadata overhead.
Outline a pub/sub layer (e.g., WebSockets, Server-Sent Events) for broadcasting changes and presence (cursors, selections). Consider using edge functions for low-latency fan-out and a message queue for reliability.
Describe how to persist documents: use a database (e.g., Postgres) for durable storage and a cache (e.g., Redis) for fast access. Discuss snapshotting and compaction to manage CRDT/OT operation logs.
Explain how to scale horizontally (sharding by document ID), handle failures (retries, idempotency), and secure access (auth, permissions). Summarize key trade-offs: consistency vs. availability, latency vs. cost, and complexity vs. maintainability.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.