Author here. This came out of a production OOM in a clustered MQTT broker. The main lesson was that we had been treating different kinds of distributed state as though they all required the same consistency guarantee. Happy to discuss the incident, the ownership model, or the design trade-offs.
MQTT is a lightweight publish/subscribe protocol commonly used for IoT. Devices publish messages to topics through a broker, and subscribers receive messages from the topics they follow. Keel MQTT Gateway is the clustered MQTT broker discussed in the article
Some more thoughts on minimum requirements for a read-after-write consistency: https://software.mihvoi.ro/2026/04/2-flow-consistency-read-y...