Hash tables are one of those miraculous data structures that, once grokked, take you up a step-function in understanding modern computer science. I'm not talking about the 2018 leetcode meme of "Just solve everything in a hash table". It's more about Array chapter in CS1 where you're told "...and therefore, can retrieval ever go below O(N), or O(logN) if sorted?" and you sit there scratching your head, assuming thats reality and then BAM, the professor reveals hash tables and O(C) retrieval and drops the mic.