> I run an agency and we maintain dozens of large, mature production projects (up to ~100k lines of code each). 100k is not small, but also not particular larg

> I run an agency and we maintain dozens of large, mature production projects (up to ~100k lines of code each). 100k is not small, but also not particular large; even for one single app with highly interweaved code. My companies main codebase is around 800k lines and I consider it as middle sized. But lines of code are not the problem. The length of your code paths is it. Understanding the flow of one or two functions, ok, not that hard of a problem. Having your data flowing through some dozen functions, big problem. Complexity kills any understanding at some point. Or you need to invest unnecessary much time for it.