What does ACID actually stand for, and why do all four properties matter together?
Atomicity (all-or-nothing), Consistency (valid state to valid state), Isolation (concurrent transactions don't corrupt each other), Durability (once committed, it survives a crash). They matter together because dropping any one breaks the guarantee the others depend on — atomicity without isolation still lets concurrent transactions see each other's half-finished work.
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Database Transactions Explained: ACID, Isolation Levels, and Concurrency ControlWhat ACID actually guarantees, and how pessimistic vs optimistic concurrency control decide whether your app locks or retries under load.
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