Couchbase Server's sub-document API enhances document databases by enabling more efficient operations on specific parts of a document without needing to retrieve, deserialize, and re-upload entire documents. This feature is particularly beneficial for applications that require frequent updates to documents, such as chat logs, as it reduces network bandwidth usage and shifts the responsibility for document updates from the application to the database layer. Sub-document operations are supported in all official Couchbase Server SDKs and utilize an extension of the memcached protocol for key-value operations. These operations require a document key and a path to the sub-document within the parent document, allowing for precise modifications or queries. The SDKs, including those for Python and Java, provide methods such as `lookupIn` and `mutateIn` to facilitate these operations, and the functionality is abstracted to simplify complex queries and mutations. To learn more about implementing these operations in different programming languages, users are encouraged to consult the updated SDK documentation.