ACID

Where it fits

ACID describes transaction guarantees in many relational databases. It is a core database concept and a key comparison point for BASE and eventual consistency.

Mental model

ACID is a compact checklist for transactional correctness: atomicity, consistency, isolation, and durability.

Subconcepts

Atomicity

All changes in a transaction commit, or none do.

Consistency

A transaction preserves database constraints and valid states.

Isolation

Concurrent transactions should not corrupt each other’s behavior.

Durability

Committed changes survive crashes or restarts, often through a write-ahead log.

Common mistakes

• Treating ACID as one single guarantee rather than four related guarantees.
• Ignoring isolation levels.
• Assuming distributed systems get ACID behavior for free.

Related concepts

Transaction, BASE, eventual consistency, isolation level, write-ahead log.