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.