[dlandiak]

You are correct. TBMQ is based on Spring Boot. We use Netty (https://netty.io/) as the source of the MQTT communication, and we build the MQTT features the MQTT broker should support ourselves on top of that. Kafka is used to implement scalable, fault-tolerant solution with reliable message persistence. Additionally, it helped to gain high-throughput processing and low-latency message delivery. We store published MQTT messages, client sessions, and subscriptions, etc., in Kafka. It proved its quality in practice and with performance tests. Redis is currently used for caching in cluster mode. In our roadmap, we also have a ticket to add the ability to store MQTT messages there. So, it will be a so-called Redis integration.

Please see the architecture doc for more details: https://thingsboard.io/docs/mqtt-broker/architecture/

We have implemented TBMQ to satisfy our enterprise customers' needs. Some of them used hivemq before but decided to ask us to build a new solution (TBMQ) as they were not fully satisfied with hivemq. One of the most important advantages we provided is cluster support in our open-source version compared to hivemq.