Database TransactionsLearn from verified, runnable examples

Isolation levels, anomalies, locking, MVCC, and real-world concurrency patterns, every claim on this site is proven by code that just ran against a real database.

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verified transcript

A> BEGIN;
B> BEGIN;
A> UPDATE accounts SET balance = balance - 100 WHERE id = 1;
B> UPDATE accounts SET balance = balance - 50 WHERE id = 2;
A> UPDATE accounts SET balance = balance + 100 WHERE id = 2;
⏳ A  waiting on B's lock (row id=2)
B> UPDATE accounts SET balance = balance + 50 WHERE id = 1;
⏳ B  waiting on A's lock (row id=1)
⏵ B  ERROR 40P01: deadlock detected
A> COMMIT;
⏵ A  COMMIT — the survivor wins

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Verified, not vibed

Nothing here is hand-waved. Every transcript came out of a real Postgres or MySQL run, and CI runs them all again on every commit. The day a claim stops being true, the build goes red.

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Run it yourself

`docker compose up`, then `bun test`. Every lesson is a real scenario you can run, poke at, and break on purpose. Flip an isolation level and watch the anomaly walk right back in.

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Focused on what breaks

You already write transactions. This digs into the parts that go wrong under load: lost updates, deadlocks, phantom reads, and the fixes that actually hold up.

The curriculum

Eight chapters, each proven against PostgreSQL and MySQL. Pick a database and start anywhere.

Transactions 101PostgreSQL MySQL
Isolation levels & anomaliesPostgreSQL MySQL
LockingPostgreSQL MySQL
MVCC under the hoodPostgreSQL MySQL
Real-world patternsPostgreSQL MySQL
Transactions across servicesPostgreSQL MySQL
Pitfalls compendiumPostgreSQL MySQL
ProductionPostgreSQL MySQL