The SQLite AI offline-sync solution consists of three main components:

• SQLite Sync: Native client-side SQLite extension
• CloudSync: Synchronization microservice
• Postgres Sync: Native PostgreSQL extension

Together, these components provide a complete, production-grade offline-first synchronization stack for SQLite and PostgreSQL.

SQLite Sync is a native SQLite extension that must be installed and loaded on all client devices. We provide prebuilt binaries for:

• Desktop and mobile platforms
• WebAssembly (WASM)
• Popular package managers and frameworks including React Native, Expo, Node, Swift PM and Android AAR

Note: The latest version (v0.9.96) is not yet available in the official SQLite Sync repository. Please use our development fork instead: https://github.com/sqliteai/sqlite-sync-dev

The extension has been refactored to support both SQLite and PostgreSQL backends.

• All database-specific native calls have been isolated in database.h
• Each database engine implements its own engine-dependent layer
• The core CRDT logic is fully shared across engines

This modular design improves portability, maintainability, and cross-database consistency.

• Shared CRDT and SQLite components include extensive unit tests
• Code coverage exceeds 90%
• PostgreSQL-specific code has its own dedicated test suite

• Deep integration with SQLite — the default database for Edge applications
• Built-in network layer exposed as ordinary SQLite functions
• Cross-platform, language-agnostic payload format
• Works seamlessly in any framework or programming language

Unlike other offline-sync solutions, SQLite Sync embeds networking directly inside SQLite, eliminating external sync SDKs.

Currently implemented CRDT algorithms:

• Last-Write-Wins (LWW)
• Grow-Only Set (G-Set)

Additional CRDTs can be implemented if needed, though LWW covers most real-world use cases.

CloudSync is a lightweight, stateless microservice responsible for synchronizing clients with central servers.

• Synchronizes clients with:
  • SQLite Cloud servers
  • PostgreSQL servers
• Manages upload and download of CRDT payloads
• Stores payloads via AWS S3
• Collects operational metrics (connected devices, sync volume, traffic, etc.)
• Exposes a complete REST API

• Written in Go
• Built on the high-performance Gin Web Framework
• Fully multitenant
• Connects to multiple DBMS backends
• Stateless architecture enables horizontal scaling simply by adding nodes
• Serialized job queue ensures no job loss, even after restarts

• Metrics dashboard available in grafana-dashboard.json

• Additional logs available via the Fly.io monitoring dashboard

For the current demo, a single CloudSync node is deployed in Europe on Fly.io. If testing from other regions, latency will reflect this single-node deployment. A production deployment would use geographically distributed nodes with regional routing for global coverage.

Postgres Sync is a native PostgreSQL extension derived from SQLite Sync.

• Implements the same CRDT algorithms available in SQLite Sync
• Applies CRDT logic to:
  • Changes coming from synchronized clients
  • Changes made directly in PostgreSQL (CLI, Drizzle, dashboards, etc.)

This ensures full bidirectional consistency, regardless of where changes originate.

SQLite does not support schemas, while PostgreSQL does. To bridge this difference, Postgres Sync introduces a mechanism to:

• Associate each synchronized table with a specific PostgreSQL schema
• Allow different schemas per table

This preserves PostgreSQL-native organization while maintaining SQLite compatibility.

The PostgreSQL integration is actively evolving. Current limitations include:

• User Impersonation: The microservice currently applies server changes using the Supabase Admin user. In the next version, changes will be applied under the identity associated with the client’s JWT.
• Table Creation: Tables must currently be created manually in PostgreSQL before synchronization. We are implementing automatic translation of SQLite CREATE TABLE statements to PostgreSQL syntax.
• Row-Level Security: RLS is fully implemented for SQLite Cloud servers. PostgreSQL RLS integration is in progress and will be included in the final release.
• Beta Status: While extensively tested, the PostgreSQL sync stack should currently be considered beta software. Please report any issues; we are committed to resolving them quickly.

• CLIENT installation and setup
• CLOUDSYNC microservice configuration and setup
• SUPABASE configuration and setup
• SPORT-TRACKER APP demo web app based on SQLite Sync WASM