Electric SQL — Sync Engine for Postgres and Local-First Apps

Introduction

Electric SQL is an open-source Postgres sync engine that brings real-time data streaming to local-first applications and AI agent runtimes. Instead of polling or building custom replication, developers subscribe to shapes of Postgres data that automatically sync to clients, enabling offline-capable apps with instant reads.

What Electric SQL Does

• Streams partial or full Postgres table data to client applications in real time
• Supports shape-based subscriptions to sync only the rows and columns you need
• Enables local-first architectures where reads happen from a local cache
• Provides a simple HTTP API that works with any programming language or framework
• Handles conflict resolution and consistency for bidirectional sync scenarios

Architecture Overview

Electric runs as a sidecar service next to your Postgres database. It reads the Postgres write-ahead log (WAL) to detect changes, then serves those changes over HTTP as shape streams. Clients connect to the Electric HTTP endpoint and receive an initial snapshot followed by a continuous stream of incremental updates. The system uses logical replication internally and manages shape definitions, caching, and delivery. No changes to your Postgres schema are required.

Self-Hosting & Configuration

• Deploy as a single Docker container alongside your existing Postgres instance
• Requires Postgres 14+ with logical replication enabled (wal_level=logical)
• Configure via environment variables: DATABASE_URL, ELECTRIC_PORT, and shape definitions
• Supports horizontal scaling by running multiple Electric instances behind a load balancer
• Use the TypeScript, Elixir, or HTTP client libraries to consume shape streams

Key Features

• Sub-second sync latency from Postgres write to client delivery
• Shape-based subscriptions let you sync exactly the data each client needs
• Zero schema changes required — works with any existing Postgres database
• Built-in caching layer reduces load on the source database
• Framework-agnostic HTTP API with official TypeScript and React integrations

Comparison with Similar Tools

• Supabase Realtime — tied to the Supabase platform; Electric works with any Postgres instance
• Hasura Subscriptions — GraphQL-based; Electric provides a simpler shape-based HTTP model
• PowerSync — commercial local-first sync; Electric is fully open-source
• CRDTs / Yjs — conflict-free data types for collaboration; Electric syncs Postgres state rather than operation-based documents
• Debezium — CDC for event streaming; Electric is optimized for client-facing sync rather than backend pipelines

FAQ

Q: Does Electric replace my existing backend API? A: No. Electric handles data sync from Postgres to clients. You still use your backend for writes, authentication, and business logic.

Q: Can I use Electric with an existing Postgres database? A: Yes. Electric reads the WAL and requires no schema modifications. Enable logical replication and point Electric at your database URL.

Q: How does Electric handle large tables? A: Shape subscriptions let you sync subsets of tables using WHERE clauses. Electric only streams the matching rows, keeping payloads small.

Q: Is there support for offline-first mobile apps? A: Yes. The client library caches synced data locally so reads work offline. When connectivity returns, the stream resumes from the last known position.

Sources

• https://github.com/electric-sql/electric
• https://electric-sql.com/docs