The present invention extends to methods, systems, and computer program products for reliable messaging using clocks with synchronized rates. Embodiments of the present invention insure at-most-once delivery of messages. A source and a destination utilize clocks with synchronized rates. Messages are assigned Time-To-Live ("TTL") values such that state information is updated the source and removed at the destination when a corresponding message timer based on a TTL value expires. Accordingly, resources consumed to maintain state information at the destination can be freed up in a shorter period of time. The source can retransmit state information to the message destination if relevant state information has been removed. Message processor instance IDs insure at-most-once delivery when a message destination suffers an involuntary memory loss. Embodiments of the present invention can also be used for exactly-once-delivery, for example, when TTL values are infinite and instance IDs are not used.