I don't know how strongly I agree with this one. Quadratic algorithms are the kind of thing that bite you when you least expect it. I have seen production outag

I don't know how strongly I agree with this one. Quadratic algorithms are the kind of thing that bite you when you least expect it. I have seen production outages due to accidentally quadratic code and it is also the type of code where some users are suffering with a really slow application because they are frequently experiencing a big N even though 99% of users have a small N all the time. In most cases I would prefer to pick a less than quadratic algorithm even if it is a bit slower for the common case and a bit more complex to implement. Slow common cases get optimized, slow in rare cases often slips by the developers (who don't hit those cases) or break in production. Of course this is a tradeoff with Rule 4. If the fancy algorithm is much more complicated I will be more likely to pick the simple one even if it is quadratic and the data has the chance of occasionally being large. But by default I try to stick sub-quadratic if possible. I wrote an article about this relatively recently: https://kevincox.ca/2023/05/09/less-than-quadratic/ https://kevincox.ca/2023/05/09/less-than-quadratic/