A bank needs to ensure that after an account transfer transaction completes, the revised account balances persists even if the database system hosting the transaction becomes temporarily…

Durability is the ACID property that guarantees once a transaction is committed, the changes are permanently stored and survive system failures, crashes, or temporary unavailability. In this scenario, the committed balance updates must persist regardless of what happens to the database system afterward. This is typically implemented through write-ahead logging or similar recovery mechanisms.

Isolation ensures concurrent transactions do not interfere with each other, not that committed data survives system failures.

Atomicity ensures all operations in a transaction complete or none do, addressing completeness rather than post-commit persistence.

Consistency ensures a transaction brings the database from one valid state to another valid state, not that committed data survives downtime.