XDCR, a feature used for data replication in various scenarios such as high availability and disaster recovery, has been enhanced in Couchbase Server 6.5 to include advanced filtering capabilities. This update allows users to filter replication based on keys, values, and metadata through N1QL-like expressions, providing flexibility to meet specific business needs such as geo-fencing. The advanced filtering is categorized into expression-based filtering, allowing the use of various language constructs, and deletion filtering, which enables the exclusion of deletes or documents with TTL from replication. Users can test and validate filter expressions by specifying document IDs, and filters can be edited without interrupting replication. These enhancements improve resource utilization by allowing more precise control over what data is replicated, and they enable new use cases like creating hot and cold data clusters. Users with versions prior to 6.5 can only filter based on keys, while versions 6.5 and above offer more comprehensive filtering options.