I'm struggling with the amount of complexity. As an inexperienced SWE, I found it difficult to put everything into my head when the # of function calls (A) + # of source code files (B) to navigate reach N. In particular, if B >= 3 or A >= 3 -- because, B equals the number of screens I need to view all source code files without Command+Tab/Alt+Tab, and cognitive load increases when A increases, especially when some "patterns" are involved.

But I'm not experienced enough to tell, whether it is my inexperience that causes the difficulty, or it is indeed that the unnecessary complexity tha causes it.

Humans have a very limited amount of working memory. 3-5 items on average. A savant might be at something like 12. It is trivially easy to blow that with code. OO with code inheritance is a prime example of combinatorial explosion that can lead to more possibilities than atoms in the universe, let alone one persons ability to reason.

Watch ‘Simple made Easy’ by Rich Hickey; a classic from our industry. The battle against complexity is ever ongoing. https://youtu.be/SxdOUGdseq4?feature=shared

You should not need to read every line of code in every file and function to understand what’s going on to the level you need to solve a particular problem. You must make a decision to NOT look deeper at some point on any non- trivial code base. A good program with good names and comments in the appropriate places is what allows you to do exactly that more easily . When you see sort(usernames) in the middle of a function do you need to dive into sort to be able to understand the code in that function?? Probably not, unless you are fixing a bug in how usernames are sorted!

With that said , get good at jumping into definitions, finding all implementations, then jumping back where you were. With a good IDE you can do that at the speed of thought (in IntelliJ that’s Cmb+b, Cmd+Alt+b, Cmd+[ on Mac). I only open more than one file at the same time when comparing them. Otherwise it’s much easier to jump around back and forth (you can even open another function inline if you just want to take a Quick Look, it’s Alt+Space). Don’t use the mouse to do that, things you do all the time can be made an order of magnitude faster via shortcuts. Too many developers I see struggle with that and are embarrassingly slow moving around the code base!

Experience helps to recognize intent sooner. That reduces cognitive load. Getting lost 5 levels deep seemingly never stops being a thing, not just you.