You start with not installing Prometheus! Prom. is a full on stats grabber and display system with knobs on.

This is a single system effort and at 5MB RAM is rather tiddly and surely counts as minimal overhead. It could probably send the metrics to Prom. or make them available for scraping with minimal extra effort but I think that should be left as an exercise for the interested reader.

The thing about gathering metrics is you have to be careful that the gathering/processing system doesn't drown out the thing you are measuring!