Azure DocumentDB 0.109 Uses Native PostgreSQL Indexes to Match MongoDB Query Performance

Azure DocumentDB, a PostgreSQL extension, has demonstrated in version 0.109 that it can handle MongoDB-style queries involving filtering, sorting, and pagination using a single compound index scan. The test replicated an earlier MongoDB benchmark that highlighted the performance advantage of document models over normalized relational databases for one-to-many relationships. DocumentDB achieves this by leveraging PostgreSQL's extensibility to define native Extended RUM indexes suited for non-relational data schemas, rather than relying on standard RDBMS indexes. The execution plan confirmed that a single index scan covered all four query stages — $match, $sort, $limit, and $project — with no additional sort or filter operations required. This positions DocumentDB as a performance-compatible alternative to MongoDB for document-model workloads built on PostgreSQL.