Spring Data Couchbase 4.0, built on Couchbase Java SDK 3.0, introduces several enhancements to boost developer efficiency and manageability. This release maximizes the use of Couchbase Server 6.5 capabilities, focusing on a streamlined developer experience by reducing code redundancy through enhanced repository patterns. Key updates include the adoption of N1QL for querying, improved automatic index management with field-level indexing, and the move to a Fluent API for templates using Reactor instead of RxJava. The new version also eliminates XML-based configuration in favor of Java annotations and removes support for Views due to advancements in N1QL. The update allows developers to leverage the full range of transaction features available through the Couchbase SDK 3.0, promoting seamless integration with the Spring ecosystem.