Getting Started with Varnish Cache

Chapter 1. What Is Varnish Cache?

Varnish Cache is a so-called reverse caching proxy. It’s a piece of software that you put in front of your web server(s) to reduce the loading times of your website/application/API by caching the server’s output. We’re basically talking about web performance.

In this chapter, I’ll explain why web performance is so important and how Varnish can improve it.

Why Does Web Performance Matter?

Many people underestimate the importance of web performance. The common logic is that if a website performs well when 10 users are accessing it, the site will also be fine when 1 million users want to access it. It only takes one successful marketing campaign to debunk that myth.

Performance and scalability aren’t one and the same. Performance is the raw speed of your website: how many (milli)seconds does it take to load the page? Scalability, on the other hand, is keeping the performance stable when the load increases. The latter is a reason for bigger organizations to choose Varnish. The former applies to everyone, even small projects.

Let’s say your website has about 100 visitors per day. Not that many, right? And the loading time of a page is 1.5 seconds—not great, but not that bad either. Without caching, it might take some time (and money) to reduce that loading time to less than a second. You might refactor your code or optimize your infrastructure. And then you might ask yourself if all of the effort was worth it.

It’s also important to know that web ...