Eventual Consistency
eventual-consistency is a consistency model used in distributed-computing that guarantees that, if no new updates are made to a specific data object, eventually all accesses to that object will return the last updated value. This model is a cornerstone of distributed-systems aiming for high availability and horizontal scalability, often at the expense of immediate strong-consistency.
The concept gained significant prominence with the rise of nosql databases and is a key component of the base (Basically Available, Soft state, Eventual consistency) model, which serves as an alternative to the traditional acid properties found in relational database management systems. According to the cap-theorem formulated by eric-brewer, a distributed system cannot simultaneously provide Consistency, Availability, and Partition tolerance. By choosing eventual-consistency, systems prioritize availability and partition tolerance (AP).
Prominent implementations include amazon-dynamodb and apache-cassandra, which utilize techniques like gossip-protocol and anti-entropy mechanisms to synchronize data across nodes. Conflict resolution is often handled via last-write-wins or vector-clocks. Detailed technical discussions can be found in Werner Vogels' seminal article or the Wikipedia overview on consistency models.