1. A method comprising: receiving, by a message broker subsystem, a message intended for delivery to a recipient software application instance; querying, by the message broker subsystem, a global directory service subsystem to determine whether the recipient software application instance is registered with the global directory service subsystem; receiving, by the message broker subsystem and in response to the querying, an indication from the global directory service subsystem that the recipient software application instance is registered with the global directory service subsystem and that one or more other software application instances that are functionally equivalent to the recipient software application instance are also registered with the global directory service subsystem, the recipient software application instance and the one or more other software application instances forming a plurality of functionally equivalent software application instances registered with the global directory service subsystem; automatically selecting, by the message broker subsystem, based on the received indication, a software application instance from the plurality of software application instances for receipt of the message in accordance with a load balancing heuristic; and attempting, by the message broker subsystem, to deliver the message to the selected software application instance.