It isn't (I have one, a whole $15/year due to some ridiculous sale some months ago). Consider that it's userspace only, so kernel doesn't count. I'm running a (light-duty) nodejs app, nginx to proxy it, tmux, and two irssi instances on mine right now, with memory to spare. Light PHP works fine too (haven't tried anything heavier).

A database server or similar wouldn't work, of course.