Thijs Feryn

Evangelist at Varnish Software

Talk - Caching the uncacheable in Varnish

When the pressure is on, your application will need to scale up or scale out. Throwing servers at the problem is not a sustainable solution and refactoring is not always effective.

Caching, on the other hand, might reduce the impact of your application on the system. Unfortunately, when personalization comes into play, caching is really hard: it’s a tradeoff between caching enough variations of your content and maintaining a good hit rate.

In this presentation, we will use different techniques in Varnish to cache personalized content:

  • Using HTTP fragments such as ESI and AJAX
  • Creating cache variations using cookie values
  • Authentication in the edge
  • Fetching session data in the edge
  • Content transformation and personalization in the edge

By doing as much decision making and transformation “in the edge”, we avoid performing expensive computing at the origin, which allows us to scale and to “cache the uncacheable”.


Thijs Feryn is a "technical evangelist" at Varnish Software, the company behind the Varnish Cache open source technology. His goal is to bring technology to the people and people to technology. He focuses on bridging the gap between code and infrastructure.

Thijs is a published author at O'Reilly, he is also involved in many open source communities. He speaks, listens, writes, codes, teaches, blogs, vlogs, organizes and is above all very excited to speak at Full Stack Europe.

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