It appears to me that parallel connections block on handler.handle here https://github.com/seanmonstar/hyper/blob/master/src/server/mod.rs#L55.

This seems weird to me. I would much rather Handler: Clone, and for Handler to simply be copied for each request and handler.handle called in its own task. That way, downstream users of this library have maximum control of what concurrency forms they want.

If not, you will have to expose a stream of incoming requests to allow downstream users to decide on their own concurrency strategies.