It actually isn't too difficult to be involved in a system handling millions of requests a day or hitting the limits of the standard Rails stack as a consultant

It actually isn't too difficult to be involved in a system handling millions of requests a day or hitting the limits of the standard Rails stack as a consultant. It probably won't happen if your client is Ma's Diner and you're building them a brochureware site. Many clients are not Ma's Diner. Many projects are not brochureware sites.