# Database Transactions > Transaction behavior on PostgreSQL and MySQL, taught from transcripts of real database > runs. Every claim on this site is proven by a scenario that CI replays against pinned > engine versions on every push, and fails on any drift. ## Proofs - [Every proven transcript](https://svyatov.github.io/database-transactions/llms-full.txt): all scenarios, with the SQL, the interleaving, and the database's own output. - [Ledger](https://svyatov.github.io/database-transactions/ledger.jsonl): one JSON Lines record per scenario — path, engine, pinned version, claim, sessions, observed error codes. No schema-stability guarantee; the shape grows as the site does.