How Does CDN Caching Work?

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Have you ever wondered how Amazon is able to offer such quick delivery times for such a wide range of items? It’s because they aren’t shipping from one central location, with some packages arriving faster for some customers who are closer to the central hub. Instead, they store inventory and ship items from a vast web of smaller warehouses across the globe, significantly reducing the time it takes for your ordered items to arrive at your door. They use the CDN method.

Content delivery networks (CDN) are the digital equivalent of this innovative logistical solution, allowing access to what you want with minimal wait times. In this article, we break down how CDNs work, how they can benefit your business, and how to get started.

What is a CDN?

CDNs are the invisible structure that supports low-latency internet access. You use a CDN to store cached versions of your content that are spread across multiple geographic locations in what are called points of presence (PoPs). This geographically distributed network of proxy servers means that when a user wants to access the content stored on a CDN, that content is accessed from the closest PoP rather than a central location. Much like in the real world, reducing the distance between the customer and what they want to access decreases the time it takes to access that content. The time a user spends waiting for their browser to request content and have that request answered is called latency. The shorter the latency period, the happier the user tends to be.

How CDN caches work
Credit: Kanoha

How Does CDN Caching Work and How is it Different from Other Caching Methods? 

If you’ve used the internet, then you’ve already made use of caching, even if you haven’t realized it. Caching is one of the most effective tools website owners have to improve their website’s speed and it works by storing data locally for a fixed amount of time. The amount of time the cache is stored is governed by the time to live (TTL), which is submitted by the website when the content request is sent.

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Aside from CDN caching, the most common forms of caching are page/site caching and browser caching. 

  • Site/page caching: Site caching, also known as page caching, works through search engines, like Google, storing a static HTML version of your webpage and offering those to the user — think of it like a backup of your site/page. Using the cached version of the page rather than the live one cuts down on the number of time-consuming database inquiries and can reduce the server load by as much as 80%.

    Page caching is best suited to pages that lack dynamic content or don’t have their content updated regularly. An example of this would be a company’s About page — it wouldn’t be updated as regularly as their Blog page would be. If your site has a high turnover of content, then it may mean your users aren’t accessing your most up-to-date content from your search engine listings. Sites/pages are cached based on your cache settings. Depending on your cache tool (for example, WP Fastest Cache), you can exclude specific pages from being cached or even enable a setting which refreshes your cache when a new and existing page has been saved, so the most recent version is cached. 
  • Browser caching: Browser caching is a form of page caching where the data is stored on the user’s computer by their web browser in what is commonly referred to as a “cookie.” When the user first accesses a page, their browser downloads content from that page and stores it locally on their computer.

    When they next access that page, the browser checks if the page has been marked updated. If it hasn’t been updated, it shows the user the version stored on their own computer, drastically reducing the load time.

    The downside of browser caching is that not everyone is comfortable with data being stored on their computer by their browser. The uptick in the use of tracking cookies, fears about data privacy and target marking, and the advent of GDPR has led to many users disabling browser caching.
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So How is CDN Caching a Better Alternative?

Unlike browser or page caching, CDN caching works well for dynamic websites with regular content updates and sidesteps user concerns about data being stored on their machines. Using CDN caching stores content (such as images, videos, or webpages) in proxy servers that are located closer to end users than origin servers, resulting in reduced latency and increased user satisfaction, without the downsides of traditional caching methods.

What Are the Benefits of CDN Caching?

Google has repeatedly emphasized the importance of page speed when it comes to SEO rankings. There is also a causal link between page speed and user satisfaction. 

Research by Google has indicated that 53% of mobile users will bounce from any site that takes longer than three seconds to load. If the page takes up to ten seconds to load, the probability of that user bouncing rises to 128%.

There are also benefits of using CDN caching beyond just faster loading times. Investing in CDN caching can help you:

  • Handle high load periods as the traffic is balanced between multiple proxy servers.
  • Reduce overall bandwidth usage.
  • Increase page speed.
  • Have an effective response to DDoS attacks.
  • Reduce user bounce rates.
  • Provide geographically localized coverage at no cost.

How Do You Get Started?

The good news is that about half of all internet traffic is already being served by CDN suppliers, and nearly all of them offer a free plan with paid options for larger companies. Popular CDNs include StackPath, CloudFlare, and CloudAccess

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Once you’ve contracted with a CDN supplier and connected your site, the process is actually quite simple. Take a look at your chosen CDN’s knowledge base for instructions since they may vary depending on which website platform you’re using. 

Hopefully, you now understand how CDN caching can be an effective tool for your website. It might sound daunting to get this implemented, but it’s really relatively easy. Speaking from experience, most CDN suppliers have support teams and documentation so that in a few minutes, you can be enjoying all the benefits that CDN caching can offer you.