The Reactor Pattern's present in a lot of production infrastructure (Nginx, Eventmachine, 0mq, Redis), yet not very well understood by developers and systems fellas alike. In this talk we'll have a look at what code is doing at a lower level and also how underlying subsystems affect your event driven services. Below the surface : system calls, file descriptor behavior, event loop internals and buffer management Evented Patterns : handler types, deferrables and half sync / half async work Anti patterns : on CPU time, blocking system calls and protocol gotchas