MQTT Retained Messages, Persistent Sessions Are Not Historians
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Global – October 28, 2026 -- Neither MQTT retained messages nor persistent sessions can guarantee complete production history, so industrial operators who need every measurement must add application-level buffering and a historian, according to an engineering analysis of the OASIS MQTT 5.0 specification.
Retained messages deliver the latest state to new subscribers
A retained message gives a subscriber the last retained value on a topic when it subscribes. In the example of a packaging line publishing to plant/line2/packer/status, a new maintenance display receives the retained RUNNING state without waiting for the next live publication, provided the message is still available and the subscription's retain-handling settings permit delivery.