Eventual Consistency

Eventual consistency is one of the consistency models used in the domain of parallel programming, for example in distributed shared memory, distributed transactions, and optimistic replication. It means that given a sufficiently long period of time over which no changes are sent, all updates can be expected to propagate eventually through the system and all the replicas will be consistent. While some authors use that definition, others prefer a stronger definition that requires consistency to be reinforced, even in the presence of continuing updates, reconfigurations, or failures. Thus, eventual consistency means that for a given accepted update and a given replica, eventually, either the update reaches the replica, or the replica retires from service.

This database terminology makes assurances about the data state which are BASE (Basically Available, Soft state, Eventual consistency), this stands in contrast to other, more traditional relational databases whose data has ACID (Atomicity, Consistency, Isolation, Durability).