Advanced CDN Caching Techniques for Optimizing Website Performance

February 6, 2024
Ann Oliver

With the demand for reliable, high-performing, and faster-loading websites continuing to soar, companies are increasingly turning toward Content Delivery Networks (CDNs).  

In today's interconnected world, CDNs have become the cornerstone of seamless knowledge sharing, augmented visitor experience, and accelerating website growth with a high-performance network.

In this article, we will offer a round-up of advanced CDN caching techniques that can boost your website performance. 

What is Caching?

Caching is the process of temporarily storing a subset of transient data in high-speed data storage facilities. The aim is to reuse computed or previously retrieved data and cater it to users faster than is possible by serving from the data’s primary storage location. A cache is usually hardware such as RAM (Random-access memory) correlated with software components.  

What is CDN Caching?

A CDN or Content Delivery Network is a globally distributed network of servers and data centers strategically located in different geographic locations. 

CDN caches static content, such as images, videos, scripts, or CSS files, in these web servers and data centers. So when a visitor opens a webpage and requests content, the CDN server most proximal to that user serves them with the cached content. It thus reduces the distance between an end-user and the server delivering content to that user. 

CDN caching improves loading speed by limiting latency - the time a webpage takes to load upon a user's request to open it. 

CDN Caching Components:

Two critical components of CDN caching are edge servers and cache control.

Let's go through them briefly.

  • Edge Server: An edge server is each of the dispersedly located and networked servers that operate in a coordinated manner to temporarily store cached content as near as possible to a requesting client machine.
  • Cache-Control: Cache-control is the tactic you adopt to store in and retrieve from an edge server effectively. Several factors, such as cache expiration time, content type, and location of the server, may influence your decision.

How Does CDN Caching Work?

The CDN caching is the amalgamation of a slew of techniques. Let's break down the operating process of CDN caching.

User Request and Edge Server Selection

When a user requests content from a website or web application, the CDN serving that website receives an HTTP request from that user's browser. The CDN then considers factors, such as server load, location, and network speed, and searches for the geographically nearest edge server. The request is sent to that server.

Cache Lookup and Content Retrieval

Upon receiving the request, the edge server starts to search for that content in its local cache storage. If the desired content is identified there, the edge or caching server immediately delivers it to the requesting user. Otherwise, the content is retrieved from the origin server or a nearby edge server and delivered to the end users. 

Cache Invalidation and Content Expiration

CDNs have cache invalidation and expiration strategies in place to ensure no cached content is outdated. There are two options available for cache invalidation - manual and automatic invalidation. The manual cache invalidation can be initiated by the CDN provider. 

In this process, specific control panels and API provided by the CDN can be used to initiate the invalidation process. While in the manual process, providers can delete cache based on their requirement, the automatic invalidation is set to be triggered when certain events take place, for example, modification in the original content. 

On the flip side, cache-control headers regulate the content expiration process by fixing the cache expiration rules such as expiration time, "time to live" (TTL), etc.

Advanced CDN Caching Techniques

Consider implementing the following advanced caching techniques and strategies to make the most of the system.

Serve Cacheable Content

Even though some CDNs cache dynamic content by applying a range of rules such as smart caching tactics, edge-side includes, etc., CDNs are mainly designed to cache static content. 

Hence, to enhance the performance and loading speed of your website, ensure catering static content with CDN caching. 

Unlike dynamic content produced on the server side, static content is bigger, can remain cached for longer, and is less frequently edited. When you cache static content at the edge server, you get the chance to reduce the load on the origin server and allow it to generate only dynamic content. The result is faster delivery to users, augmented scalability, and reduced bandwidth usage, ultimately enhancing user experience. 

Set the Cache Lifetime Tactfully

Until the cache lifetime ends, the CDN edge server sends a cached version of the requested content to the users without accessing the origin server. It directly impacts the freshness of the content you serve to your website visitors through the CDN. 

Carefully setting cache lifetime ensures your content is never stale or outdated and is revalidated periodically. 

Hence, appropriately set this parameter to strike a fair trade-off between updated content and the CDN speed benefits. 

Segment Caches

Cache segmentation is the process of categorizing website content into multiple segments based on a slew of factors - user demographics, ages, preferences, etc. Segmenting cached content is a key tool to elevate user experience by serving them with personalized content.  

For example, let's assume you have a user base from a specific geographic location. Now, implementing cache segmentation would allow you to deliver local versions of content to that user base, based on their language, preferences, or cultural nuances. The result is fortified user satisfaction, doubled down by enhanced user experiences. 

Use Custom Cache Keys

If you need to update your website content more than often or deliver personalized content tailored to your users' preferences, using a custom cache key stands as a strategic imperative. 

It is because to exert more control over the access and management of cached static content, there is no better way than using custom keys. In addition, with these keys, you can designate specific identifiers on cached content to trigger seamless recovery and delivery of content from origin servers as per your requirements. Furthermore, they enable you to add or delete any combination of hosts, protocols, and query strings effortlessly. 

To sum up, using custom cache content helps enhance content delivery and enable optimization of the caching system, thus ultimately boosting website/web app performance.

Leverage Browser Caching

Another key CDN caching tactic is to use browser caching. It leverages cache-control headers that empower client-side caching and define the timeframe a browser should hold cached content in its local cache. 

Benefits of CDN Caching

Performance

One of the key benefits of CDN caching mentioned by enterprises is its capability to boost website performance. 

Case in point: Websites relying on CDN caching to deliver their content to end users have reported a reduction of 50% in load times, or even more in some cases. CDN caching improves and enables faster page loading by:

  • Reducing the distance between end users and servers storing content
  • Compressing file sizes
  • Optimizing edge server infrastructure, so it can respond and deliver content to users faster.

Improves SEO Performance

Another benefit of CDN caching businesses can't overlook is that it helps webpages rank higher in the search engines. Caching stands as a strategic imperative when it comes to augmenting the Core Web Vitals and overall Google Page Experience ranking factor by uplifting client perception and interaction with your web pages. 

Bringing content closer to the end users reduces latency and enables faster webpage loading. This increased website speed enables a fortified browsing experience as visitors spend more time on a webpage.

Case in point: According to studies, 1 in 4 users abandon a website that takes more than 4 seconds to load. Even a delay of a single second can take user satisfaction down by 16% while 64% of disappointed customers do not return to a slow website again.

Mobile-friendliness is a ranking signal in Google and Bing's algorithms. CDN caching limits load time for a website in mobile devices, where less bandwidth and slower connection speeds are common. The result is enhanced interactivity of the loading time, optimized content delivery to mobile devices, and elevated website experience that helps boost SERP ranking. 

Improve Reliability and Redundancy

Caching content in the CDN edge servers ensures faster and uninterrupted service delivery despite hardware failure or server congestion. Even if an edge server fails, CDN enables optimal internet traffic distribution and ensures content cached in that server is delivered to the requesting users via another nearby functioning server. 

On the other hand, CDN plays a pivotal role in maintaining uninterrupted content delivery even when a website experiences a sudden increase in internet traffic. 

During high traffic times, CDN offloads the origin server and spreads the lion's share of the load among multiple edge servers to ensure your website is always up and running and content is available without interruption. This uninterrupted, faster content delivery ensures improved reliability and redundancy. 

Greater Security

Another benefit of CDN caching worth mentioning is its capability to protect websites from DDoS attacks. When a hacker tries to execute a DDoS attack, it floods the website with a bulk of malicious traffic that exhausts and overwhelms the website. 

Thus, legitimate users find it difficult to access content from this site. CDN, during sudden peaks, acts as a buffer. It redistributes this load and ensures the malicious traffic is filtered out and cannot access the origin server.

Ann Oliver
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