Recently, Varnish Technical Evangelist Thijs Feryn led a webinar covering Varnish Configuration Language (VCL), the unique programming language that powers all of our software, as well as the popular open source Varnish Cache. For those who weren’t able to attend the webinar, you can watch it here.  

This week’s episode is about VCL — the Varnish Configuration Language — which is used to define your own caching policies in Varnish Cache and Varnish Enterprise, and the number one feature in Varnish.

Varnish offers a multitude of modules that extend standard VCL capabilities for specific use cases and improve the overall user experience. These modules are written in C, and we call them VMODs for short. You can see the full list here.

A few weeks ago, I wrote and post introducing the concept of Hit-for-Miss and I received a few questions about it because "Hit-for-Pass" is much more common on the interwebz, and it looks like it could do something similar, and I completely omitted it last time. What's up with that?

Let's embark on a short chronological journey explaining how HfM and HfP (as the cool kids call them) came to be, how they are different and why you should care.