Offline-First Architecture with Capacitor & SQLite: Complete Guide
How to build resilient mobile apps with local SQLite storage, background bidirectional synchronization and CRDT conflict resolution.
Why offline-first is mandatory for mission-critical apps
In mobile applications deployed for field technicians (energy, industrial maintenance, logistics), network connectivity is rarely guaranteed. Losing inspection data because of an underground tunnel or a dead zone is unacceptable for enterprise stakeholders.
Building an "offline-first" application is not just about adding an in-memory cache: it is about designing the app so that the local embedded database is the primary source of truth, with the network acting as an asynchronous replication layer.
1. Storage Engine: Why Embedded SQLite?
While `localStorage` and `IndexedDB` are convenient in a web browser, they have critical limitations on mobile: - OS eviction risks (iOS purges IndexedDB when storage is low). - Lack of full ACID transactions. - Poor performance on heavy datasets (+100k rows).
With Capacitor, the `@capacitor-community/sqlite` plugin delivers true native SQLite power on iOS and Android, including hardware SQLCipher encryption.
2. The Bidirectional Sync Pattern
To prevent data loss and race conditions, synchronization is split into 3 steps: 1. **Optimistic Local Mutation**: Every UI action writes directly to local SQLite and logs an entry in an `outbox_queue`. 2. **Connectivity Listener & Batch Sync**: Network listeners trigger grouped API calls when online. 3. **Deterministic Conflict Resolution**: Vector clocks or CRDT algorithms merge states automatically without overwriting changes.