Start by clarifying requirements and scope (e.g., real-time collaboration, offline support, scale). Then outline the high-level architecture, focusing on core components like document storage, real-time sync, and conflict resolution. Dive into key technical challenges such as operational transformation, consistency models, and trade-offs between latency and durability.
Pro tip: Emphasize the trade-offs between consistency and availability, and how Google Docs uses operational transformation (OT) to achieve real-time collaboration. Mention that OT is complex but necessary for low-latency editing, and contrast it with CRDTs as an alternative.
Ask questions to understand the expected scale (e.g., number of concurrent editors, document size), features (real-time collaboration, offline mode, version history), and non-functional requirements (latency, consistency, availability).
Sketch the main components: client apps, load balancers, API gateways, document service, collaboration service, storage (e.g., blob store for document snapshots, database for metadata), and pub/sub for real-time updates.
Explain how edits are propagated using WebSockets or long polling, and how operational transformation (OT) or CRDTs resolve conflicts. Discuss the role of a central server for ordering operations and maintaining consistency.
Describe how documents are stored: periodic snapshots in a blob store (e.g., Colossus) and incremental operations in a log. Explain version history and how to reconstruct a document at any point.
Discuss partitioning by document ID, replication for availability, and caching. Address trade-offs: consistency vs. latency, OT vs. CRDTs, and how to handle offline edits and sync.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.