Lots of it is stuff that I've picked up over the years. I work(ed) in the maps industry for the last 4 years or so, until I was laid off about a week and a half ago. I do interact with OSM a little bit in the docker image generation but the servers (geocoder, tileserver, routing server) all pre-process their data to turn it into a format that's useful for each server's specific purpose. So none of the HTTP requests that my demo server is responding to right now actually directly touch any OSM data.
Most of the OSM data processing is done in the Makefile, but beware that it was very hastily written so it's not a perfect example: