Strong consistency

Content sourced from Wikipedia, licensed under CC BY-SA 3.0.

Strong consistency is a guarantee used in concurrent programming, such as in distributed shared memory or distributed transactions. It means every read returns the most recent write and all parts of the system observe the same value at the same time. Put differently, there is a single, agreed order of updates, so after a write finishes, all future reads see that value. This idea is often called linearizability. Strong consistency makes reasoning about data easier, but it can limit performance and availability because coordinating updates across machines is required. It is different from weak or eventual consistency, where reads can show stale or differing values for a while.