Using an event-driven architecture like Nginx, HTTP-kit is very, very fast. It comfortably handles tens of thousands of requests/sec on even midrange hardware. Here is another test about how it stacks up with others.
It's not only fast, and efficient! Each connection costs nothing but a few kB of memory. RAM usage grows O(n) with connections.
Clean, Simple, Small
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.
Sync or Async
Synchronous is simple. Asynchronous is fast & flexible. With HTTP Kit you get the best of both with a simple API that let's you mix & match to best fit your use case.