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Cover image for Zero-Downtime DB Sync: Resilient Database Streaming Migration CLI
Tarek Mohamed
Tarek Mohamed

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Zero-Downtime DB Sync: Resilient Database Streaming Migration CLI

#database #devops #opensource #python

Migrating multi-gigabyte production databases between servers or database engines (e.g. MySQL to PostgreSQL, or SQLite to cloud databases) traditionally required taking applications offline for hours.

zero-downtime-db-sync is an open-source CLI utility designed to perform live, streaming schema and data migrations with continuous replication and zero application downtime.

GitHub logo seotarek / zero-downtime-db-sync

A resilient, zero-downtime streaming database migration and replication CLI tool for MySQL, PostgreSQL, and SQLite.

Zero-Downtime DB Sync ⚡

License: MIT Python Version Engines

A resilient, chunk-based streaming database migration and live data replication CLI tool. Safely migrate gigabyte-scale databases across servers with automatic network checkpointing, zero RAM bloat, and minimal table lock time.

💥 The Problem It Solves

  • Dump & Restore Fails on Large Tables: Traditional mysqldump or pg_dump creates massive files that lock read/write traffic and timeout on unstable networks.
  • Network Dropouts Waste Hours: If an SCP transfer drops at 99%, you typically have to restart from scratch.
  • RAM Spikes Crash Instances: Reading whole tables into memory crashes low-spec VPS or containers.

Zero-Downtime DB Sync streams rows in configurable primary-key batches, tracks the last committed ID in a persistent checkpoint file, and resumes seamlessly if interrupted.

🚀 Key Features

  • Chunked Streaming: Consumes memory in predictable O(chunk_size) bounds using server-side cursors.
  • Fault-Tolerant Checkpointing: Tracks migration progress down to the exact row ID; automatically resumes after network disconnects.
  • Cross-Engine…
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⚙️ How It Works

  1. Initial Parallel Snapshot: Streams existing table rows in concurrent batches using cursor-based pagination.
  2. Change Data Capture (CDC): Listens to WAL / binlog change events to capture real-time writes occurring during the migration.
  3. Atomic Verification: Performs row count and checksum audits across source and destination tables before initiating switchover.

Install and run via CLI:

db-sync migrate --source "mysql://user:pass@host/db" --target "postgres://user:pass@host/db" --live
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Contribute and view documentation on GitHub:
👉 https://github.com/seotarek/zero-downtime-db-sync

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