[tyre]

I agree with everything except the five seconds note. Web pages loading in fives seconds is an awful experience.

Optimizing expensive queries not only improves the user experience (be it web or api or whatever) but also can open up entire usecases that otherwise wouldn’t be practical. Five second queries are a primate candidate for DOS attacks, whether intentionally malicious or by users spamming refresh, retry, etc.

[Izkata]

I think he meant shaving only 5 seconds off of the 200 second query.

[nicoburns]

Maybe, but shaving almost 5 seconds off a 5 second query can be quite realistic for some pathological ORM queries. I use ORMs for the simple cases, but it's definitely worth cutting them out in the complex ones.