I wish more web developers would come to this conclusion. It's so frustrating to see people trying to save 50ms by optimising slow SQL queries or fixing slow code paths. Meanwhile the user is waiting over 5 seconds to load a page with a bloated DOM, inefficient CSS, synchronous JavaScript, etc.

If your back-end is slow, just cache it and forget about it. Front-end is almost always the bottleneck (the exceptions to this rule being near-real-time dynamic sites like New Relic or GoSquared).