Couchbase Server 4.5 Developer Preview introduces a range of new features aimed at enhancing querying efficiency, advanced data access, and administration capabilities. Key updates include the Query Workbench for executing ad-hoc queries directly from the admin console, extended join syntax for faster JOIN operations, and integrated full-text search based on the Bleve project. The release also offers partial document updates, memory-optimized global indexes, and array indexing to improve performance and flexibility. Additionally, it provides new tools for query profiling, high-performance backup and restore, and secure communications via X.509 certificates. The preview is intended for development use only and feedback is encouraged to refine the final release.