I have worked on algorithmic trading where you basically stare at instructions and try to ensure the CPU does not stall on branches, that memory is accessed in

I have worked on algorithmic trading where you basically stare at instructions and try to ensure the CPU does not stall on branches, that memory is accessed in a strided pattern recognizable to the CPU and that there are no more concurrent patterns that CPU can coordinate, that memory written does not by accident belong to another core, etc. What is "mystery" in the article is actually bread and butter of anybody who tasked to seriously optimize a piece of non-trivial code.