I went straight to the data model and storage layer, which in hindsight was the wrong move.
Start by clarifying requirements and scale, then outline a high-level architecture that separates real-time collaboration (WebSocket, CRDT/OT) from storage and sync. Dive into data modeling, conflict resolution, and trade-offs, and wrap up by discussing scalability, consistency, and failure handling.
Pro tip: Emphasize the trade-offs between operational transformation (OT) and conflict-free replicated data types (CRDTs), and how you'd choose based on consistency needs and complexity. Also, mention how you'd handle offline editing and eventual consistency, as Google values robust distributed systems thinking.
Ask questions to understand expected user count, document size, latency requirements, offline support, and consistency needs. This sets the stage for design decisions.
Sketch the main components: clients, real-time sync service (WebSocket), storage layer, and conflict resolution engine. Explain how data flows between them.
Describe how to represent notes (e.g., as a sequence of operations or a tree) and choose a conflict resolution strategy (OT or CRDT). Discuss trade-offs.
Detail the protocol for propagating changes, handling concurrent edits, and ensuring low latency. Mention presence and cursor tracking.
Discuss partitioning, replication, and how to handle network partitions, offline edits, and server failures. Address consistency models (strong vs eventual).
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.