> A better metric for deciding where you should focus the most effort on code quality is not frequency of modification, it is frequency of appearance in the run

> A better metric for deciding where you should focus the most effort on code quality is not frequency of modification, it is frequency of appearance in the runtime call-graph. On th flip side, a lot of code that isn't common in the main codepath often exists to fix edge case bugs that people have lost context on. In my experience, this code is a landmine with an unknown blast radius, only touch it with a 10-foot pole and only when you absolutely must.