The gist of it is that it's a simple REST interface, and we liked Varnish in front of nginx. But we've outgrown that now, and we're working on something that's a hash-sharded HAProxy or nginx reverse proxying to HAProxy in front of varnish in front of HAProxy in front of HttpFS in front of HDFS. And also there's another nginx between varnish and the backend HAProxy to handle rewriting pants' REST requests to HttpFS requests