A Rubyist's guide to Big-O notation - Honeybadger Developer Blog

I don't have a degree in computer science, and it's okay if you don't either! Lots of us Rubyists don't have formal computer science credentials. So for a long time, I avoided learning about big-O notation. It looks a little too much like higher math. I mean just look at something like: O(N^2). Come on! Instead, I learned a few useful rules of thumb for thinking about scalability: Finding a specific item in a Hash is faster than finding an item in a similarly sized Array Avoid nested loops Watch out for accidental database queries when generating lists in your views These rules are pretty useful, but unless you understand WHY they work, you're going to find yourself making mistakes and having inexplicable performance problems. Big-O notation doesn't have to be scary. Once you understand some basic principles, you'll find it to be a straightforward way of thinking about how certain chunks of code scale.