Hey HN! I built Velo to solve a problem I kept running into: testing database migrations and debugging production issues without copying around massive database dumps or waiting for slow clones.
The core idea: use ZFS copy-on-write snapshots to branch PostgreSQL databases the way you branch Git repos. A 100GB database branches in ~2 seconds and takes ~100KB of space initially. Each branch is a complete, isolated PostgreSQL instance running in Docker.
How it works:
- Runs CHECKPOINT to flush PostgreSQL buffers (ensures consistency)
- Creates a ZFS snapshot (filesystem-level, instant)
- Clones the snapshot to a new dataset (CoW means no data copying)
- Spins up a new PostgreSQL container pointing at the clone
The mental model is: Project = Git repo, Branch = Git branch. Commands like `velo branch create api/test-migration` or `velo branch reset api/dev`.
I also added point-in-time recovery using WAL archiving, so you can create branches from specific timestamps (e.g., "5 minutes before the incident").
Requirements: Linux + ZFS + Docker.
Built using Bun and TypeScript.
Let me know what you think :)
