Stop memoizing Hash lookups in Ruby

When a method performs a slow operation, memoizing the result using instance variables is a useful optimization. However, I’ve often seen people (including myself, sometimes!) reaching for memoization for things that don’t need to be optimized. One common example is when there’s a class that wraps a Hash object. Hashes in Ruby are quite well optimized, so do you really need to memoize the result of the hash lookup? Let’s benchmark and find out.