Redundant mechanism in a push-to-talk (PTT) realtime architecture. Redundancy is provided in core delivery systems, which are employed for the emulation of "walkie-talkie" service with circuit switched duplex calls in the carrier network. The disclosed architecture provides for geographic and/or realtime mated redundancy. In one implementation, realtime redundancy is offered in an active-active scenario, although other scenarios are possible. Similarly, redundancy is provided in a roaming gateway implementation of the PTT network.