HTTP Kit
Clojure HTTP server/client library with WebSocket support
.../sec on even midrange hardware. Here is another test about how it stacks up with others. It's not only fast, but efficient! Each connection costs nothing but a few kB of memory. RAM usage grows O(n) with connections. Written from the ground-up to be lean, the entire client/server is available as a single ~90kB JAR with zero dependencies and ~3k lines of (mostly Java) code. Synchronous is simple. Asynchronous is fast & flexible.