Currently all methods on DBDirectClient go through the full networking and command execution layers to perform basic i/o against the database. This has caused many issues in the past including but not limited to problems with access control, curop tracking/profiling, write concern and maxTimeMs handling, command metadata management, etc. It also means that any code using DBDirectClient requires linking in a huge amount of the mongoDB codebase. The public API of DBDirectClient isn't bad, it's the implementation that goes through networking and command execution just to do basic reads and writes to documents in the database. If instead DBDirectClient bypassed those layers and called directly into the query API, it would be much easier to use correctly and much more useful.