How do you design a resilient offline-first iOS application architecture?

Offline-first architecture prioritizes local persistence and sync strategies over immediate network dependency.

An offline-first system stores all user actions locally (Core Data or SQLite) and synchronizes with backend when network is available. It requires conflict resolution strategies (last-write-wins, CRDT-like merging), background sync queues, and retry mechanisms. Data consistency and idempotency become critical. UI must be driven entirely from local state to ensure responsiveness.