[munk-a]

I would mention that you're not bound to a single language so writing the guts of the business logic in something like PHP, Ruby or server-side node might be fine - you'd just hook up the performance sensitive bits up to a library written in a compiled language.

In fact I think there are certain organizational benefits to partitioning your language use by skills required to maintain that section of code. When you're a startup there's no benefit at all, but as companies grow you can use that to smoothly transition into separate teams with different expectations around testing and feature flexibility.