I used OpenResty as the core for an experimental HTTP routing service at my previous job. The idea was to maintain host:port pairs for HTTP services in Redis and use a small bit of Lua code to look up the right place to proxy a virtual host to. It worked well enough, but never got deployed because we were concerned about the Redis SPOF. Now-a-days it wouldn't be that big of a deal.

That said, the nginx/lua combo is wonderful to work with. I got the core of that thing working in just a few hours.