I also found it an interesting post in that it kind of inadvertently proves that for most situations you shouldn't optimise to this extent.

Meaning, yes, the OP got impressive performance improvements but the code is also completely unreadable and utilises unsafe code sections which could expose you to security problems/memory leaks/memory corruption. Not to mention they've recreated and will need to maintain an in-house version of the Dictionary class.

Their first optimisation (from Enumerator to List and Any() to Count()) are something every codebase could use. Most of their other optimisations make the code a maintenance minefield.

Plus programmers are expensive. Hardware is cheap. Why spent time on harder code to write that's also harder to maintain in the medium to long term when instead you could just throw money at hardware and call it a day? Just food for thought, not really a criticism in and of itself.

PS - Please don't take this post too seriously. I am not really being critical, just playing devil's advocate. I actually enjoyed the linked article a lot.