Testing a migration against a toy database proves almost nothing. Database Lab Engine is an open-source platform that clones production-sized PostgreSQL databases in seconds, giving every developer, CI job, and query experiment a full-fidelity copy without waiting hours for a restore or paying to store ten of them. The trick is thin cloning: copy-on-write snapshots taken on ZFS or LVM let a one-terabyte database materialise as a writable branch in about ten seconds, with dozens of independent clones sharing one physical dataset until their changes diverge. Teams point CI at a fresh clone for every migration, so 100 percent of schema changes get rehearsed against real data shapes and volumes before they touch production; analysts get disposable copies for testing query rewrites and index ideas; and a bad experiment costs one delete, not one restore. Clones are managed through a web UI, API, and CLI, draw from self-managed Postgres or managed sources on RDS, Cloud SQL, and Supabase, and carry popular extensions in their containers. Resets, upgrades, deletion protection, retention rules, and resource quotas keep the fleet tidy as it grows into branches and snapshots numbering in the dozens. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Apache-2.0 licensed.