“What’s the fastest way of doing this?” - you might ask yourself during development. Sure, you can guess - but how do you know? How long would that function take with a million elements? Is that tail-recursive function always faster? Benchmarking is here to give you the answers, but there are many pitfalls in setting up a good benchmark and analyzing the results. This talk will guide you through, introduce best practices, and surprise you with some results along the way. You didn’t think that the order of arguments could influence its performance...or did you?