XDCR, or Cross Data Center Replication, is a high-performance replication technology used in Couchbase to replicate data between clusters, enhancing distributed systems with improved performance, high availability, and fault tolerance. XDCR operates asynchronously, maintaining data consistency across clusters through eventual consistency, and is characterized by its low latency, independent scalability, infrastructure agnosticism, and topology awareness. It features a simplified setup, flexible topologies, resilience to network failures, and optimizations for bandwidth conservation via compression and network throttling. XDCR leverages Couchbase's Database Change Protocol (DCP) for efficient data state communication, supporting both pessimistic and optimistic replication modes. Additionally, XDCR can resume replication from checkpoints after interruptions and is designed to function smoothly without centralized coordination, allowing for decentralized replication and high throughput. Concerns about duplicate replication in hub-and-spoke models are mitigated by DCP, which ensures efficient and optimal data propagation.