cluster_commands_helpers.h contains a collection of free-standing functions that encapsulate shard targeting and command execution against shards. Under the hood, they use MultiStatementTransactionRequestsSender, which in turn uses AsyncRequestsSender. There is another API, called AsyncRPC, which takes typed command objects instead of raw BSONObject's, and is largely incompatible with AsyncRequestSender. Some of our infrastructure (e.g. sharding_ddl_util) uses this other API. This ticket is to consider adding minimal support for this API in cluster_commands_helpers.h .