I mean, every programmer who funnels through university understands map reduce, and that helps on multi-core threading up to system job running.

But there is a limit, usually in the persistence and caching layers. What you'll find is that those "large scale deployments" are going to have a -lot- of internal cache systems and I can pretty much guarantee that the services running those caches and persistence will not be written in ruby.

You can make anything* scale, but how many CPU cycles you need to burn to get the functionality you want is a matter for the finance department.

If you're running in a lossy business, you can bet that those CPU cycles will begin to cost more than developer velocity is worth, because servers are an eternal and ongoing cost.

On the flip side if you make more money than the infra+devs cost, then nobody is going to hound you for wasting 2x 3x the cost. Because "it's the cost of doing business" is easier to justify when you're cash positive.