This is the kind of question where you think you know what to say and then you open your mouth and realize you don't.
Start by clarifying requirements (e.g., scale, latency, consistency) and then propose a high-level architecture using a client-server model with operational transformation (OT) or CRDTs for conflict resolution. Walk through the design of key components like real-time communication, document storage, and concurrency control, while discussing trade-offs.
Pro tip: Emphasize the trade-offs between OT and CRDTs, and mention that Google Docs uses OT. Also, discuss how to handle network partitions and offline editing, showing awareness of real-world challenges.
Ask questions to understand the scale (number of concurrent users, document size), latency expectations, consistency needs, and offline support. This shows you can scope the problem effectively.
Outline the main components: clients, real-time collaboration server, document storage, and possibly a pub/sub system. Explain how clients connect via WebSockets and how updates are propagated.
Discuss conflict resolution strategies: Operational Transformation (OT) or Conflict-Free Replicated Data Types (CRDTs). Explain how they work, their trade-offs, and why OT is suitable for Google Docs-like systems.
Describe how to represent the document (e.g., as a sequence of operations or a tree) and how to persist it. Mention using a database like Bigtable or Spanner for scalability and consistency.
Address scaling the collaboration server (e.g., sharding by document ID), handling failures (replication, failover), and ensuring low latency (edge servers, caching).
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.