I know compilers can do some crazy optimizations but wouldn't have guessed it'll transform something from O(n) to O(1). Having said that, I dont still feel this has too much relevance to my actual job for the most part. Such performance knowledge seems to be very abstracted away from actual programming by database systems, or managed offerings like spark and snowflake, that unless you intend to work on these systems this knowledge isn't that useful (being aware they happen can be though, for sure).

Also this series is targeted towards more of a beginner audience to compilers, thus its likely to be suprising to the audience, even if not to you.

For you are essentials.

You and the juniors you hire must have a deeper knoledge than him.

Maybe you have much more experience than Mr Godbolt in compiliers.

If you mean graph coloring restricted to planar graphs, yes it can always be done with at most 4 colors. But it could still be less, so the answer is not always the same.

(I know it was probably not a very serious comment but I just wanted to infodump about graph theory.)