From my understanding, the C10K concept is more a thread problem than a RAM limitation. It happens when each request create its own thread on server (as in Apache or IIS). Computer have problem to run 10,000 threads in same times: too much time is consumed by the OS to find the one thread that is not blocked/locked or waiting for datadabase results.

Node.JS solve this problem by doing all in Asynchronous way (in only one thread). GO solve this pb by doing clever threads (goroutine). Functional programming seems to be very good on this issue (no need of lock mecanism and light thread).

It's not based on netty:

> {:dependencies [[org.clojure/clojure "1.5.1"]]}

netty is in the dev dependencies, but for benchmarking only I would guess.

[edit] This project is one of the best thing that happened in the web area in clojure recently imho. Not only it is a game changer in performance/resource use, but it makes websocket and async in general trivial to use and actually production ready (same goes for its client). Some would mention Pedestal but it forces you to learn quite a few abstractions and is totally alien compared to the rest of the clojure web ecosystem and also only supports a single async "protocol" (SSE). But pedestal is about a full stack experience, integration with the client etc, so it certainly will attract other users.