There is a person running a Python program on one of our servers, which is something that people do regularly. As far as I can tell, this person's Python program is using some Python framework that supports on the fly reloading (often called hot-reloading) of changed Python code for at least some of the loaded code, and perhaps much or all of it. Naturally, in order to see if you need to hot-reload any code, you need to check whether a bunch of files have changed (at least in our environment, some environments may be able to do this slightly better). This person's Python code is otherwise almost always idle.

The particular Python code involved has decided to check for a need to hot-reload code once every second. In our NFS fileserver environment, this has caused one particular fileserver to see a constant load of about 1100 NFS RPC operations a second, purely from the Python hot-reload code rechecking what appears to be a pile of things every second. These checks are also not cheap on the machine where the code is running; this particular process routinely uses about 7% to 8% of one CPU as it's sitting there otherwise idle.

(There was a time when you didn't necessarily care about CPU usage on otherwise idle machines. In these days of containerization and packing multiple services on one machine and renting the smallest and thus cheapest VPS you can get away with, there may be no such thing as a genuinely idle machine, and all CPU usage is coming from somewhere.)

To be fair, it's possible that the program is being run in some sort of development mode, where fast hot-reload can be potentially important. But people do run 'development mode' in more or less production, and it's possible to detect that. It would be nice if hot-reload code made some efforts to detect that, and perhaps also some efforts to detect when things were completely idle and there had been no detected changes for a long time and it should dial back the frequency of hot-reload checks. But I'm probably tilting at windmills.

(I also think that you should provide some sort of option to set the hot-reload frequency, because people are going to want to do this sooner or later. You should do this even if you only try to do hot reloading in development mode, because sooner or later people are going to run your development mode in pseudo-production because that's the easiest way for them.)

PS: These days this also applies to true development mode usage of things. People can easily step away from their development environment for meetings or whatever, and they may well be running it on their laptop, where they would like you to not burn up their battery constantly. Just because someone has a development mode environment running doesn't mean they're actively using it right now.