I'd love to see functions too, and am not sure your concerns are necessarily dealbreakers. Optimization should be easier if you use something like node-burrito for the low hanging fruit, and node.js developers are already aware that long synchronous loops should be avoided in a single-threaded environment.

I think you convinced us to give functions a second look, as long as we can have a good story for auth, i can't see why we shouldn't add them, given the right optimizations are in place. They could be very powerful. https://github.com/pubsubio/pubsub-hub/issues/3