A discussion of key-based purging in Varnish, covering both the Xkey VMOD by Varnish Software and Fastly's Surrogate Key feature. Presented at the High-Scale Varnish Meetup in San Francisco at Pantheon Systems on 2016-05-05. A recording of this talk is available at https://www.youtube.com/watch?v=yRPoLBEtD9Y