Offline First Mobile Architectures: SQLite, ElectricSQL & CRDT Based Conflict Free Synchronization

Conventional REST and GraphQL architectures require round trip network requests before updating mobile UI state. When latency spikes or connectivity drops, apps freeze or drop user input. In local first architecture, UI components bind reactively to an embedded SQLite database. Reads and writes execute in less than 1 millisecond locally, providing instant UI feedback.

Synchronizing mobile client SQLite databases with backend PostgreSQL instances traditionally required fragile custom sync engines. ElectricSQL solves this by establishing bidirectional, active active replication streams via Postgres logical decoding. Changes written to client side SQLite sync to the cloud over WebSockets, while cloud mutations stream instantly to subscribed mobile clients.

Concurrent offline modifications across multiple devices inevitably cause data collisions. By implementing Conflict Free Replicated Data Types (CRDTs) such as Observed Remove Sets (OR Sets) and Last Write Wins Registers (LWW Registers) equipped with hybrid logical clocks (HLC), client applications deterministically converge to identical state without server arbitration.

Mobile storage is constrained. We implement rolling tombstone compaction to purge deleted record logs and partition sync shapes so mobile clients only download data relevant to the active user profile. All SQLite databases are encrypted at rest using SQLCipher with keys securely stored in the iOS Keychain or Android Keystore.