Eventual consistency is a consistency model used in many large distributed databases which requires that all changes to a replicated piece of data eventually reach all affected replicas; conflict resolution is not handled and responsibility is pushed up to the application author in the event of conflicting updates .
Eventual consistency is a specific form of weak consistency; the storage system guarantees that if no new updates are made to the object, eventually all accesses will return the last updated value . If no failures occur, the maximum size of the inconsistency window can be determined based on factors such as communication delays, the load on the system, and the number of replicas involved in the replication scheme .
A few examples of eventually consistent systems:
- Asynchronous master/slave replication on an RDBMS e.g.