Couchbase Server 4.6.0 Developer Preview introduces a range of new features and enhancements across various functionalities, including cross datacenter replication, security, query optimizations, data manipulation tools, and full-text search capabilities. A key highlight is the introduction of a timestamp-based conflict resolution for cross datacenter replication, allowing for the seamless resolution of document conflicts by comparing timestamps. The release also enhances security with pluggable authentication modules for centralized password management, although this feature is limited to Linux platforms and enterprise users. N1QL, Couchbase's query language, sees significant updates with new functions for manipulating date/time values and string tokenization, alongside performance optimizations. Data import and export are streamlined with new tools for handling CSV and JSON files, and full-text search capabilities are bolstered with faster indexing and query processes, customizable sorting options, and improved index type mapping. The release supports new operating systems, including MAC OSX Sierra and Windows 10 Anniversary Edition, and performance improvements are also made to the full-text search engine and its underlying library, bleve.