What are DuckDB's ACID transaction guarantees?

Despite being an embedded, analytics-focused database, DuckDB provides full ACID (Atomicity, Consistency, Isolation, Durability) transaction guarantees for operations against its own storage format, the same fundamental correctness guarantees expected of a traditional transactional database.

BEGIN TRANSACTION;
INSERT INTO accounts VALUES (1, 100);
UPDATE accounts SET balance = balance - 50 WHERE id = 1;
COMMIT;

Transactions in DuckDB either fully complete or have no effect at all (atomicity), the database moves between valid states according to defined constraints (consistency), concurrent transactions within the same process don't see each other's uncommitted changes (isolation, via MVCC), and committed changes survive a crash (durability), since DuckDB persists changes to its on-disk file format rather than keeping everything purely in memory.

This matters because it means DuckDB isn't limited to purely read-only analytical querying, an application can also reliably insert, update, and delete data within transactional boundaries, which is part of what makes DuckDB usable as an actual application-embedded database rather than strictly a query engine for static files.