The goal of this ticket is to audit all “special” read/write paths and see if we can identify any sharding-related bugs where MongoDB is not upholding the guarantees given by the MongoDB Server read and write semantics doc.

“Special” read/writes paths include any read paths excluding the standard read paths used for executing FindCommandRequests on sharded clusters, and any write paths excluding the write paths used for executing update/delete on sharded clusters.

We expect most of these "special" read/write paths are used by aggregate pipeline stages (ex. $merge).