What is ACID design?

ACID is an acronym that describes the four key properties of a database transaction: Atomicity, Consistency, Isolation, and Durability. Atomicity ensures that a transaction is all‑or‑nothing; if any part fails, the entire transaction is rolled back. Consistency guarantees that a transaction brings the database from one valid state to another, preserving all defined rules and constraints. Isolation means that concurrently executing transactions do not interfere with each other; the intermediate states of a transaction are invisible to others. Durability ensures that once a transaction commits, its changes are permanently stored, surviving system failures. These properties are fundamental for reliable data management in relational databases and many NoSQL systems that emulate transactional semantics. For example, when transferring money between bank accounts, ACID guarantees that the debit and credit happen together, the account balances remain consistent, concurrent transfers do not corrupt data, and the final state persists even if the server crashes.