The document reviews the features of MongoDB 4.4 and Couchbase 6.5, emphasizing their advancements in query language capabilities. MongoDB 4.4 introduces enhancements to the MongoDB Query Language (MQL), including a new $UnionWith aggregation stage and custom aggregation expressions using Javascript, although these are considered verbose and potentially error-prone. Couchbase 6.5, released earlier in the year, supports a wide range of SQL set operations and has previewed SQL and Javascript functions across N1QL expressions, enhancing developer productivity with features like window functions. Both platforms have made notable improvements in search functionality, with MongoDB's $search based on Lucene available only on its Atlas service, while Couchbase offers a SEARCH() function integrated with its N1QL optimizer. Additionally, MongoDB now supports creating collections and indexes within non-sharded transactions, whereas Couchbase has introduced distributed transactions for Java SDKs, though not for N1QL statements.