Nginx's modularity and tolerance/embrace of plugins is absolutely amazing. I use a combination of openresty[0], lua scripting, and third party modules in our API servers (coincidentally, one that talks directly to Redis) and it's still one of the fastest, best pieces of software in our stack.

I understand the concern, but if it ends up being half as flexible (and I already love me some Redis) I can only see good things.

I was talking more of my experience than C projects in general. However, I'd expect a smaller percentage of C projects to support modules compared to Ruby given the differences in the language.