Let’s compare: 1000 parallel connections 100k requests yesod : 7658 recs/sec Errors 85808 Timeouted 0 Mine:: 12699 recs/sec Errors 0 Timeouted 0 10k connections, 100k requests: yesod: 5205 recs/sec Errors 81152 Timeouted 3842 Mine: 8160 recs/sec Errors 0 Timeouted 46 Sources: Yesod: / HomeR GET |] instance Yesod HelloWorld getHomeR :: Handler () getHomeR = do number <- liftIO (randomIO :: IO Float) let txt = pack $ "hello world " ++ show number sendResponse (txt:: Text) main :: IO () main = warp 3838 HelloWorld Mine: import Sockets import Foreign.C.String import Data.IORef import Control.Concurrent main = do ref <- newIORef 1 s <- socket defaultCallbacks { constructor = \ci -> set_cb ci defaultCallbacks { done_connected = binded ref, done_reading = process } } pl <- epoll 1000 pl1 <- epoll 1000 pl2 <- epoll 1000 pl3 <- epoll 1000 listen s "8080" pl_accept pl s pl_accept pl1 s pl_accept pl2 s pl_accept pl3 s let run pl = do forkIO $ run_loop pl (-1) run pl run pl1 run pl2 run_loop pl3 (-1) binded ref pl s = do i <- readIORef ref putStrLn $ "connection nr:"++show i writeIORef ref (i+1) pl_read pl s return 0 process pl s buf len = do str <- peekCStringLen (buf,fromIntegral len) ip <- client s str1 <- peekCString ip putStrLn $ "from "++str1++" \ngot "++str write pl s "Hello World!!!\r\n" return 0 if using -threaded performance is *worse*. Greetings, Branimir.