Couchbase Server 4.0 introduces significant new features, such as N1QL, a query language based on SQL designed for querying JSON data with a flexible schema, enabling rich queries against Couchbase documents. N1QL allows users to perform complex queries that resemble SQL while accommodating JSON's flexible structure, offering operators to enhance data manipulation. The Couchbase .NET SDK supports N1QL, providing seamless integration with the ability to use it alongside LINQ for type safety, code completion, and compile-time checking. Developers can explore these functionalities through open-source resources available on GitHub and NuGet, with "try-cb-dotnet" offering step-by-step tutorials to facilitate learning. Other notable features in this release include filtered XDCR for selective data replication and LDAP security for improved access management.