The new META().plan functionality and the new Plan UI combine in Couchbase Server 5.0 to improve the N1QL writing and profiling process, allowing developers to better understand how their queries are being executed and identify potential performance issues. The plan includes a tree of operators that combine to execute the N1QL query, providing detailed information about the query cost without going into detail of each operator. This feature is available in the Query Workbench and can be enabled by setting the profile feature for the entire node or on a per-request basis. Developers can also use this feature to identify potential performance issues such as slow indexing or high servTime values, which may indicate that the indexer or key/value service cannot keep up with the load. By adding more nodes to the cluster if necessary, developers can address these issues and improve overall query performance. The new functionality is available in the February 5.0.0 developer release of Couchbase Server and provides valuable feedback opportunities for developers to share their experiences and suggestions.