Breaking Change According to https://github.com/mongodb/specifications/blob/master/source/server-selection/server-selection.rst#use-of-read-preferences-with-commands , mongosh was not behaving properly when calling runCommand. In the current mongosh version, runCommand is considering the readPreference specified either by using setReadPref or in the connection string. This was the main issue of some inconsistent behaviours. In the new mongosh version, runCommand is not going to consider anymore the readPreference provided globally, either by setReadPref or in the connection string. It will accept a new parameter, an object of type RunCommandOptions: export declare type RunCommandOptions = { /** Specify ClientSession for this command */ session?: ClientSession; /** The read preference */ readPreference?: ReadPreferenceLike; /** @deprecated This is an internal option that has undefined behavior for this API */ willRetryWrite?: any; /** @deprecated This is an internal option that has undefined behavior for this API */ omitReadPreference?: any; /** @deprecated This is an internal option that has undefined behavior for this API */ writeConcern?: any; /** @deprecated This is an internal option that has undefined behavior for this API */ explain?: any; /** @deprecated This is an internal option that has undefined behavior for this API */ readConcern?: any; /** @deprecated This is an internal option that has undefined behavior for this API */ collation?: any; /** @deprecated This is an internal option that has undefined behavior for this API */ maxTimeMS?: any; /** @deprecated This is an internal option that has undefined behavior for this API */ comment?: any; /** @deprecated This is an internal option that has undefined behavior for this API */ retryWrites?: any; /** @deprecated This is an internal option that has undefined behavior for this API */ dbName?: any; /** @deprecated This is an internal option that has undefined behavior for this API */ authdb?: any; /** @deprecated This is an internal option that has undefined behavior for this API */ noResponse?: any; /* Excluded from this release type: bypassPinningCheck */ } & BSONSerializeOptions; For example, if we want to run `hello` with a readPreference `secondaryPreferred` we would do: Enterprise replset [primary] test> db.runCommand({ hello: 1 }, { readPreference: 'secondaryPreferred' }) { topologyVersion: { processId: ObjectId( "64dccf2b9129f981534d8598" ), counter: Long ( "4" ) }, hosts: [ 'localhost:27017' , 'localhost:27018' , 'localhost:27019' ], setName: 'replset' , setVersion: 1, isWritablePrimary: false , secondary: true , <<< HAS BEEN READ FROM A SECONDARY primary: 'localhost:27017' , me: 'localhost:27018' , << FROM THIS SECONDARY If no readPreference is specified, `primary` will be used, ignoring any other global configuration, including setReadPref or readPreference in the URL.