Per Buer is the CTO and founder of Varnish Software, the company behind the open source project Varnish Cache. Buer is a former programmer turned sysadmin, then manager turned entrepreneur. Runs, cross country skis and tries to keep his two boys from tearing down the house.
In this article, Per Buer will talk about cache invalidation specifically to readers who already work with Varnish Cache. To learn more about it, you’ll find background information in “Speed Up Your Mobile Website With Varnish.”
A cache miss depends on two factors: the volume of traffic and the average time to live (TTL), which is a number indicating how long the cache is allowed to keep an object. To have a high TTL, we need to be able to invalidate objects from the cache so that we avoid serving stale content. With Varnish Cache, there are myriad ways to do this. You’ll explore the most common ways and how to deploy them.