I started with the obvious stuff, last-write-wins conflict resolution, a central sync service, device polling intervals.
Start by clarifying requirements (real-time latency, conflict resolution, offline support) and scale. Then design a client-server architecture with a sync service, using WebSockets for real-time push and a conflict-free data model (e.g., last-write-wins with versioning or CRDTs). Finally, discuss trade-offs around consistency, latency, and battery life.
Pro tip: Emphasize the importance of handling offline scenarios and conflict resolution gracefully, as Kindle users often read in airplane mode. Mention that Amazon's Whispersync already solves this, but propose improvements like using CRDTs for better merge semantics.
Ask about expected latency (real-time vs near-real-time), number of devices per user, offline support, and conflict resolution needs. Confirm scale (millions of users, billions of devices).
Propose a client-server model with a sync service that stores user progress and bookmarks. Clients connect via WebSockets for real-time updates, with fallback to long polling or push notifications.
Design a data model with versioning (e.g., vector clocks or timestamps) and choose a conflict resolution strategy like last-write-wins or CRDTs. Discuss how to handle concurrent updates from multiple devices.
Define message formats for updates (e.g., JSON over WebSocket), include device ID, timestamp, and position. Describe how the server broadcasts updates to other devices and how clients apply them.
Discuss trade-offs: real-time vs battery life, consistency vs availability. Address scalability with sharding by user ID, caching, and using a pub/sub system like Kafka or SNS.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.