emqx/emqx

EMQX is a category-defining infrastructure project with over a decade of development. Its defensibility stems from the extreme technical complexity of scaling to millions of concurrent MQTT connections using Erlang/OTP, a niche but powerful stack for fault-tolerant distributed systems. It has massive community and enterprise momentum, making it the de facto open-source choice for IoT messaging. Frontier labs focus on intelligence/compute rather than connectivity protocols, making the risk of direct displacement by them very low.