Couchbase Server 4.0, now in developer preview, introduces significant enhancements such as the N1QL query language that combines SQL and JSON to simplify application coding by enabling SQL-like operations on JSON data. The release also features Global Secondary Indexing (GSI) for faster, scalable queries, and Multi-Dimensional Scaling (MDS) to optimize performance by allowing separate scaling of data, indexing, and query workloads. Additionally, it offers improved security compliance with features like native LDAP integration and detailed auditing, alongside native SDKs for easier integration and connectivity options via ODBC and JDBC drivers. The release is still under development, encouraging user feedback to shape its final form, with resources available for developers to explore and test these new capabilities.