Well, it's not irrelevant, but it's common practice. Of course bad practice. Seen it myself. Facebook and others might be able to choose the better approach but a lot of badly managed companies / projects choose the last resort solution to through out millions of dollars for hardware as they're incapable of fixing the problems properly. Those projects are politically screwed, so they often sell their solution to buy expensive hardware as success. Sounds ill, I know ...

Nice misquote. Put some numbers out.

The evolution of a project as I've seen it at large companies:

1. Build slow app in high level language, build out your infrastructure with cacheing and load balancing, CDNs, etc. 2. See what is slow / can be optimized in the current language. 3. Re-implement critical pieces in a lower level, more efficient language.

Facebook is building HHVM to eliminate step 3. You can have a bunch of people continuously re-implementing critical pieces, or you can have a smaller bunch of people make the higher level language more efficient once and have all your projects, current and future, benefit. And you also save money from the inefficient language.

I'd like to see the numbers on how much, say, using Ruby with all the optimizations - load balancers, cacheing, etc. will cost you over using Java - also with optimizations. I'm not convinced by a random person's statement that it is that huge of an impact, especially considering factors like finding programmers for optimized languages, productivity differences in programming in the different languages, etc.