How does Redis handle data consistency in distributed systems?

Redis provides eventual consistency using asynchronous replication and requires application-level strategies for strong consistency.

Redis replication is asynchronous, meaning writes are first applied to the master and then propagated to replicas. This can lead to replication lag and temporary inconsistencies. In distributed systems, developers often use strategies like write-through caching, quorum-based writes, or Redis transactions with WATCH to maintain consistency. For critical operations, Redis can be combined with other systems (like databases) to ensure strong consistency guarantees.