Available returns a ReadConcern that requests data from an instance with no guarantee that the data has been written to a majority of the replica set members (i.e.

Linearizable returns a ReadConcern that requests data that reflects all successful majority-acknowledged writes that completed prior to the start of the read operation.

Local returns a ReadConcern that requests data from the instance with no guarantee that the data has been written to a majority of the replica set members (i.e.

Majority returns a ReadConcern that requests data that has been acknowledged by a majority of the replica set members (i.e.

Snapshot returns a ReadConcern that requests majority-committed data as it appears across shards from a specific single point in time in the recent past.

A ReadConcern defines a MongoDB read concern, which allows you to control the consistency and isolation properties of the data read from replica sets and replica set shards.