What is 'eventual consistency' in a database?

Eventual consistency refers to a model in distributed databases where, after a period of time, all updates to a particular piece of data will propagate through the system and all copies of that data will become consistent. This means that while immediate consistency is not guaranteed, the system is designed to ensure that all changes will eventually be reflected across all copies.

This model is often used in environments where high availability and partition tolerance are prioritized over immediate consistency, such as in many NoSQL databases or distributed systems. Eventual consistency is essential in scenarios where the system must handle concurrent updates and network partitions, as it allows the database to remain operational while ensuring that data will converge to a consistent state eventually.

The other options present concepts that either define immediate consistency or suggest a lack of changes, which do not align with the principle of eventual consistency. Thus, the correct choice captures the essence of how distributed databases manage the trade-off between availability and consistency.