From the article: "When performance wasn't a consideration from day one, inefficiency becomes endemic, corrupting every square mibbibyte of the project. Why not

From the article: "When performance wasn't a consideration from day one, inefficiency becomes endemic, corrupting every square mibbibyte of the project. Why not iterate a giant array instead of using hashes?" Spending 5 minutes choosing the right algorithm every time you write a component isn't premature optimization, especially if you know to within an order of magnitude or so what N is. If you have no idea what N is, then go with the simplest implementation that works at the time. (That assumes your design doesn't tie a bunch of internal component decisions together, in which case I must say, "good luck with that.") In any case, the time to optimize is most likely after you've written some tests to verify the code is correct. I've seen too many cases where people spent a lot of time making something really complicated--and completely untested--run faster, and then later said, "Now how can we make this correct?"