As you’ve seen throughout this book, Couchbase Server can replicate bucket data internally. This allows Couchbase to prevent data loss in the event of node failure. However, there are several cases in which you might like to replicate your data to another cluster. For example, you might have to provide your application with cluster-level failover, otherwise known as a hot backup. Another reason for cluster-level replication is often found in applications that are distributed across data centers in different geographic regions. Or perhaps you want to provide separate environments for development, QA, and production but keep the data synchronized between all three. For such applications, it makes sense to replicate your data between clusters, providing local replicas of your data. Cross-datacenter replication (XDCR) is a bucket-level, cluster-to-cluster replication. You can use XDCR to synchronize data in a bucket between different clusters.