Came here to say this X-Accel-Redirect (Nginx sendfile), if supported by Haskell is the way, it is zero copy and will dramatically help in many cases. If you

Came here to say this X-Accel-Redirect (Nginx sendfile), if supported by Haskell is the way, it is zero copy and will dramatically help in many cases. If you are modifying the body is one of the cases where it doesn’t work.