Blog > Varnish Cache

Advantages and Disadvantages of Cache Warming with Varnish and CDNs

Daniel Bartholomew | March 26, 2018 | Varnish Cache, Caching

What is Cache Warming? Cache warming is a process that some engineers follow to try and improve the performance of their website. Many websites depend on caches. A cache is a system that stores portions of the website in high-performance storage to help avoid reading from systems that have poor performance or to reduce pressure on bottlenecks in the system. Caches exist in many places in your website setup. For example, there are caches within your CPU, built into your database, and even within specific applications like Redis or Memcached.

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Varnish Cache - Expiration vs Eviction

Shaun Guo | February 26, 2018 | Varnish Cache, Caching

Varnish Expiration vs Eviction When investigating cache hit rates in Varnish Cache it is important to differentiate between objects that have expired from the cache and objects that were evicted from the cache. An expired asset is one that has exceed the sum of its TTL(time-to-live) value and grace period and should be removed from the cache. An evicted asset, however is one that is removed from the cache because Varnish Cache has run out of space in memory and must delete a piece of data prematurely. The former is a regular part of the caching process, the latter can cause unnecessary performance problems.

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How to Measure Varnish Cache Performance

Danny Randa | December 07, 2017 | Varnish Cache, Caching

So you’ve installed Varnish Cache, now what? How can you tell whether or not it gave you the performance improvement you expected? You’d be surprised how many people get Varnish up and running and end up flying blind. Without proper logs and metrics you have few ways of knowing if Varnish is actually doing what you think and giving you the performance benefits you are looking for. In addition, Varnish often needs to be tuned after the initial setup to ensure that new items are properly cached and you are accounting for the behaviors of your specific users in your cache setup.

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How to Install Varnish Cache

Danny Randa | December 01, 2017 | Varnish Cache, Caching

Varnish Cache has quickly grown to be a popular reverse proxy software for accelerating HTTP requests and caching static and dynamic content. It’s an incredibly powerful way to speed up websites, increase scalability, and reduce server costs. Getting started, however, can be a bit of a headache. Before you dive into the fundamentals of VCL let’s take a quick look at everything you need to know about installing Varnish Cache.

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Debugging Varnish VCL

Jason Stangroome | October 09, 2017 | Varnish Cache, Performance

Varnish Cache’s Configuration Language (VCL) can be very approachable to get started with basic caching behaviour for your website. However, once you start to leverage the power of VCL to achieve the best possible performance for your site, you can find yourself in a situation where some HTTP requests don’t appear to be behaving how you expect. Varnish has some great tools to help you troubleshoot.

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Varnish 5.2 Already Available on

Glenn Slaven | September 18, 2017 | Varnish Cache, Performance

Varnish Cache released their latest 5.2 version late last week and it is already available on’s globally distributed Application Edge.

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Announcing Virtual Waiting Room

Stewart McGrath | September 18, 2017 | E-commerce, Performance, Varnish Cache is pleased to announce another feature to help websites stay online when extreme traffic peaks arrive. A Virtual Waiting Room can ensure that your website stays up and serving customers when an extreme traffic event would otherwise have caused a complete outage.

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Troubleshooting Varnish Cache 503 Guru Meditation Error

Roxana Elliott | August 08, 2017 | Varnish Cache

If you use Varnish Cache on your website or are visiting a website that caches content with Varnish, chances are at some point you will come across the Varnish server error: Error 503 Service Unavailable / Guru Meditation with an XID number. A 503 error means that the web server trying to be reached is unavailable - this could be because it is overloaded, down for maintenence, or not fully functional for another reason.

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The Guide to Varnish Cache

Roxana Elliott | August 02, 2017 | Varnish Cache, Caching

We’re pleased to release Varnish Cache 101: A Technical Guide to Getting Started with Varnish Cache and VCL. Varnish Cache is a powerful HTTP accelerator that is popular due to its speed and flexibility, as it allows users to cache both static and dynamic content, resulting in extremely fast page load times. However, it can be difficult for new users to learn how Varnish works and Varnish Configuration Language.

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Improve Time to First Byte with HTML Streaming

Stewart McGrath | July 12, 2017 | Varnish Cache, Caching is pleased to introduce HTML Streaming, a new feature which allows for dramatic improvement of the Time to First Byte and Start Render time without needing to cache the full HTML document. While already gives users the power to cache full HTML documents and provides a Developer PoP for testing before going to production, we understand some websites don’t want to change their source code to allow for the full HTML Document to be cached. That’s where HTML Streaming comes in.

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Front End Optimizations for Better Performance

Roxana Elliott | July 05, 2017 | Varnish Cache, Caching

When it comes to page load time, there are two distinct parts that any website manager or developer should consider: The back end load time and the front end load time. Back end load time is important because it is the time a website visitor is waiting before any information from your website is sent to their browser.

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How to Cache Static Content with Varnish Cache

Roxana Elliott | June 29, 2017 | Varnish Cache, Caching

Varnish Cache is a popular tool due to how quickly it delivers content from the cache and how flexible it can be. Using Varnish’s domain-specific language, Varnish Configuration Language (VCL), users can cache both static and so-called “dynamic” content, also known as the HTML document.

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Varnish Cache Tutorial with

Danny Randa | June 13, 2017 | Varnish Cache, Performance

Varnish Cache is a modern, flexible HTTP accelerator that speeds up websites by caching both static and dynamic content. Varnish is an open source tool that can also be deployed on content delivery solutions such as, and it has grown in popularity in the past several years because it is faster and more configurable than older solutions like Nginx and Squid.

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What is a Varnish Cache Hit for Pass?

Matthew Johnson | May 31, 2017 | Performance, Varnish Cache

When using Varnish Cache one of the most important things you need to understand is how and why various requests get labelled as they do. A “cache hit” and “cache miss” are easily understood - a cache hit is a request which is successfully served from the cache, and a cache miss is a request that goes through the cache but finds an empty cache and therefore has to be fetched from the origin.

Read More Adds Varnish Cache 5.1.2 to Content Delivery Grid

Roxana Elliott | April 20, 2017 | Varnish Cache, Performance is pleased to announce we have added several additional Varnish Cache versions to our Content Delivery Grid. When setting up with, users can choose the reverse proxies they run and the versions of those proxies. is committed to offering unmodified open-source software and not “locking in” users to a specific reverse proxy version. That’s why we now offer 7 Varnish Cache versions and additional options with VCL for static caching and Magento-specific capabilities.

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Under the Hood - What Reverse Proxy is your CDN using?

Danny Randa | December 16, 2016 | CDNs 101, Caching, Varnish Cache

One of the most remarkable things about the CDN market in the 20 years since Akamai launched the first Content Delivery Network is how little attention has been paid to the technology these companies are built on. When you consider the function they serve, it is somewhat understandable. Your website is slow, you pay for a CDN and suddenly it is faster. You don’t really care how it works as long as you get the desired result.

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Varnish Cache for Magento 2 - Configuration Suggestions

Matthew Johnson | December 09, 2016 | Magento, Varnish Cache, Caching

Magento 2, a complete reconfiguration of the popular ecommerce platform, is built for speed and is a vast improvement in website performance over Magento 1.x versions. One of the major differences in Magento 2 is that it is built to integrate with Varnish Cache, an extremely fast http-accelerator that is configurable to cache a variety of content, from static objects such as pictures to Javascript snippets and even full HTML documents.

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Announcing Traffic Overload Prevention

Melissa Kilbourne | November 22, 2016 | E-commerce, Performance, Varnish Cache

A top concern for websites is staying online during spikes in traffic. Businesses spend lots of money from their marketing budget to attract customers to their website, however, if the website cannot handle the amount of traffic it can go offline during these traffic peaks and lose all of the potential revenue from customers in the middle of transactions.

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Magento 2 - Key Differences and Setting up Caching

Matthew Johnson | October 10, 2016 | Magento, E-commerce, Performance, Varnish Cache

Magento 2 was released to merchants almost a year ago, and is a complete platform overhaul from Magento 1.x versions, rather than an update. There are several core differences between Magento 1.x and Magento 2 that are important for businesses and Magento developers and businesses to understand.

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Why Scalability Matters to Your Ecommerce Site During the Holidays

Roxana Elliott | September 30, 2016 | Caching, E-commerce, Performance, Varnish Cache

Improve user experience on your ecommerce site during the Holiday Season We’ve spoken a lot about the importance of speed for your website and why it’s especially crucial for ecommerce sites going into the holiday season. Many studies have shown that improved web performance leads to more pages viewed, more products viewed, and most importantly, increased cart conversions and revenue.

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Cache Fundamentals Part 2 - What Content to Cache and Why

Roxana Elliott | September 16, 2016 | CDNs 101, Caching, Varnish Cache

We previously went through the fundamentals of caching, what it is, why it’s important for faster web pages, better SEO, and reduced server costs, and what the differences are between a browser cache and a cache installed on a web server. Now we’ll go through some information on what type of content is typically cached, how Content Delivery Networks or CDNs are related to caching, and some tools to cache your own web data and improve the performance of your website.

Read More Joins Magento's Technology Partner Program

Roxana Elliott | September 08, 2016 | E-commerce, Magento, Performance, Varnish Cache

We are pleased to announce that has become a Magento Select Technology Partner, a level of partnership that includes many other top-tier technology solutions designed to help Magento eCommerce customers get the most out of their websites. We’re excited about this partnership because we recognize Magento as the leading eCommerce solution for all kinds of businesses, from small boutiques to large, recognizable brands, and we have already been building our own tools to integrate seamlessly with the Magento system.

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Varnish WAF Options

Daniel Bartholomew | September 07, 2016 | Varnish Cache, Security

It’s common that a modern web site will want the advantages of Varnish’s excellent programming model in tandem with a WAF.

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The cost of HTTP 404 Page Not Found

Jason Stangroome | August 26, 2016 | Caching, Security, Performance, Varnish Cache

Reducing 404 error pages on your website Do you know how many resources are consumed by your origin web servers to determine that a requested URL is non-existent and render the Not Found response page? Many site owners cannot answer this question, and most of the time this is fine because a well-managed site will rarely need to serve a 404 under normal conditions.

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How music-streaming site Orfium used Varnish Cache to improve page performance

Michael Petychakis | August 22, 2016 | Varnish Cache, Case Studies, Caching, Agile, Performance

Background: Implementing Varnish Cache with Orfium is a new music platform which combines some of the best features of existing platforms such as SoundCloud, Bandcamp and Beatport, allowing users to share their tracks, promote them and sell downloads. In addition, it promises to introduce a range of interesting new options for music makers and labels, including the payment of streaming royalties and the ability to upload DJ mixes while compensating all artists whose music is included.

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Magento Varnish Metrics 101

Melissa Kilbourne | July 21, 2016 | Varnish Cache, Magento recently released a new Magento extension that provides visibility for business managers to see their magento varnish cache metrics without having to login to the application. You can get the extension for your Magento website by going to the Magento Marketplace.

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Canonical bare domains and cookies

Jason Stangroome | June 21, 2016 | Varnish Cache, Caching, Security

Suppose you bought the domain name “” for your website. Will your visitors enter or just the bare domain in their browser’s address bar to access your site?

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Integrating Magento with's CDN for Performance Metrics

Daniel Bartholomew | May 06, 2016 | Varnish Cache, Caching, Magento

Magento loves Varnish Cache, and Magento 2 especially loves Varnish Cache.

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Contributing back to the community

Jason Stangroome | April 21, 2016 | Varnish Cache, Caching

Varnish Cache was the first reverse proxy offered by and, for many of us, it is our favourite because it always just works and gives great results.

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Reducing the risk of change

Jason Stangroome | April 14, 2016 | Varnish Cache, Caching


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Heading to 2016 Magento Imagine?

Stewart McGrath | April 09, 2016 | Magento, Varnish Cache,

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