Cognitive load is what matters

This was my main takeaway from A Philosophy Of Software Design by John Ousterhout. It is the best book on this subject and I recommend it to every software developer.

Basically, you should aim to minimise complexity in software design, but importantly, complexity is defined as "how difficult is it to make changes to it". "How difficult" is largely determined by the amount of cognitive load necessary to understand it.

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.

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!