Node-RED as a back-end... Node-RED IS a back-end as it is a web server for the dashboard. i.e. the Front-End would be the dashboard. You can use multiple instances (installs) to do tasks that are unrelated, and perhaps on different servers, then bring the data to a main instance. We have instances which are running on Windows Server that handle data from other "nodes" and TCP devices and MQTT, of course. The MQTT broker is on a separate Windows Server with SQL Server to store data from all systems.
Link nodes cannot be addressable between instances. You can do this with MQTT and you still need to serialize or name the connections. You can also do this with TCP nodes. That has much more overhead as you need to maintain connections.
What your looking to do is reinvent the wheel with the same wheel. What I would suggest is working with Node-RED as it is (Which is pretty dang great), and get familiar with what it is and does, then you can do amazing things.
