[raphaelj]

I wrote the Yesod tests for this benchmark.

It uses Warp.

Actually, the performances of Yesod are not so bad, as Play's are. Top performing frameworks (netty, vertx, go) are not web frameworks but async programming frameworks. They don't carry a lot of things around -- just push the serialized data on the raw socket output stream. Yesod/Play/Django/Rails/... on the other hand must manage routes, content types, browser headers, etc etc....