[epoxyhockey]

Ask them about database design, sockets, parallelism, map/reduce, memory allocation, etc. and you'll get blank stares.

You might have better success just advertising for someone who has experience with whatever large data requirement you are working with. Senior engineers can learn the framework if they aren't already familiar with it.

I wouldn't expect a RoR engineer to be very concerned with memory allocation, parallelism or sockets. They are busy building sexy CRUD web applications.