Show HN: Velo – Git-like branching for PostgreSQL databases using ZFS snapshots

Being able to branch from my db and merge after testing was a killer feature for me in PlanetScale. Great to see this functionality as an open source project.

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 :)