I think my first project that's still "in production" and used daily was taking an existing SVG map of a water distribution system (snowmaking and fire suppression pipelines/pumps/valves/etc at a major ski resort). I made a MQTT topic for each pump, valve and section of pipe along with some state for each (water direction, pump or valve on/off, pressures, etc). It's a website, so I used mqtt.js and jQuery to update the colours and fills of the SVG to represent the various states. It's statically hosted and there's a mqtt broker that's been running in a container, untouched for nearly 10 years now. Mqtt.js is running over a web socket, so if the state is updated, it just magically updates for everyone else.
It was early days, yeah. The other part of the project that's been depreciated now was running node 0.4, if I am not mistaken. The watermap was part of a bigger asset tracking system, node + jade templating (before jade became pug, even). The watermap was actually embedded in a jade template, but when I depreciated the other system, I ended up just copy and pasting the output from the jade file into an index.html, and everything just kept working :D
