Solid, well-researched and comprehensive article. One small correction: > Unicorn is built to cut off long running worker processes after a default of 30 secon

Solid, well-researched and comprehensive article. One small correction: > Unicorn is built to cut off long running worker processes after a default of 30 seconds via SIGKILL. This is why Unicorn says it's built for "fast clients" - because anything beyond that cut-off is subject to termination. This is not what "fast clients" refers to. Unicorn being built for fast clients means that it is only meant to serve local network clients. Or, in other words, it's not meant to communicate with end-user connections/clients directly (slow clients), rather, it's meant to run behind a proxy server like nginx or apache. The "fast client" thing is basically saying, "this is an application server, not a web server", meaning, it's good at running application code, not managing the complexities of serving web requests to public internet (slow) clients. They're called slow clients because, well, they're slow ;) They have variable quality connections, bandwidth / transfer rates, and client capabilities (http 1.0 vs 1.1, 2.0, spdy, etc). Being a fast client means you can expect that you'll receive http requests at a relatively constant rate, basically whatever the local network or file system will allow, which is extremely fast (comparatively). So, unicorn being a "fast client" just means that it's good at talking over local network connections (or, preferably, unix sockets) with a web server, and never on port 80 serving public http traffic.