[mikhailfranco]

Add MQTT to your lists of event buses.

MQTT is lightweight and fits nicely into IoT sources, backend streaming and even scalable frontend distribution to browser or mobile clients. I recently did a quick'n'dirty PoC with paho.js and D3.js for live charting in the browser.

In a pub-sub event-driven world, CQRS just means having distinct events for: Commands to do something; Query matches (CEP-style); and other Notifications that something has happened. Queries are compiled and unfolded into streaming operator graphs, delivering match events to the client. Queries and their operator graphs can be factored to share common sub-expressions (like the RETE rules algorithm).

A good start-up idea would be MQTT 'appstreamer' framework, with model-driven message formats, validation and APIs, together with pluggable engines for CEP queries, rules, workflows, constraint solvers and other business logic.