MongoDB supports multi-document ACID transactions (since v4.0 for replica sets, v4.2 for sharded clusters) — grouping operations across multiple documents/collections so they all succeed or all fail. However, MongoDB's document model often makes transactions unnecessary through atomic single-document operations.
Single-document operations are already atomic
KEY POINT: operations on a SINGLE document are ALWAYS atomic in MongoDB.
→ Because related data is often EMBEDDED in one document, many operations that would
need a transaction in SQL are a single atomic document update in MongoDB.
→ Good schema design (embedding) often eliminates the NEED for multi-doc transactions.
