If you are reading this, you must have heard the word CDN multiple times. Content Delivery Network, or CDNs, are a method of delivering your website or application content to your users faster by implementing the caching technique across the interconnected web of multiple servers over different geographical locations. CDNs are being widely used for websites or applications that are content-heavy or serve users in multiple countries.  While CDNs are implicitly good for auto-configuring the content delivery, it is wise to load test your website or application if you are using a CDN. There are many scenarios and business-specific use cases that require load testing websites that use CDNs to identified and resolve issues. We will talk about such problems later in this article.


What is a CDN and How Does it Work?

A CDN is a network of servers spanning across the globe to deliver geo-location-based content to end-users. These interconnected servers, called nodes/edge servers, are strategically placed to duplicate the content from the original server to serve a large number of users from their nearest edge servers resulting in speedy delivery of content.  Modern CDN provides the same delivery experience for both static and dynamic websites or applications. Website content such as scripts, style sheets, images, videos style sheets, videos, etc., are cached to the edge servers, and user requests are served from that edge server rather than origin server. Let’s understand it more through the following example:

Suppose you have your origin server in the United States and service users worldwide. With the use of CDN, your website content is cached on a CDN edge server in India and other countries. When a user from India makes a request to access your website, that request will be served from the nearest edge server in India. This way, response time is less than it would have been from the origin server, and your website will load faster.

The following are some significant benefits of using CDN with your website:

  • Improved website load time
  • Reduced network bandwidth cost
  • Improved content availability
  • Increased redundancy for server-fail cases
  • Improved security through DDoS prevention measures and other optimization


Why Load Testing Websites that Use a CDN is Important

CDNs are great for quick response time and faster loading of your website. If you have a website that uses a CDN and serves a large number of users from different geographical locations, load testing becomes necessary to prevent avoidable hiccups and provide a seamless user experience. The following list describes the use cases and scenarios that you need to manage with CDN-enabled website:


Third-Party Services

Many developers and testers don’t take third-party services into account for their failures. In such cases, if there is a problem with third-party resources, your website will become inaccessible, even if there is no problem with your website. For example, if static links are used for third-party services, your CDN will default on using third-party services, causing problems for your users.


Geo-location Testing

Content that requires area-specific blocking or customization needs to be tested with CDN servers to meet those requirements. Apart from that, different regions will have different loads that you need to optimize on different levels based on the load testing data.


Content-specific Testing

Suppose you have a streaming service. You need to test your CDN for videos and analyze how it affects video quality, connectivity, and accessibility of your streaming service to end-users.


Network Analysis

Load testing your websites that use CDNs will give you important data about bandwidth, response time, latency, and other network-related metrics to check how your website will behave with real-world users while serving them from the nearest edge server.



You might have paid access to some of your content. Load testing your website will help you ensure that paid content is only accessible to permitted users. Apart from that, CDNs may also have their limit for real-world loads. CDN load testing will help you make sure the accessibility and availability of your website.


SLA requirements

Every business has SLA requirements that they need to comply with. Your origin infrastructure might be good with SLA requirements, but if you are using a CDN, it is essential to load test your website with CDN to ensure that all SLA requirements are met.

Load testing is vital for high-performing websites that use CDN because if your website is affected by issues related to CDN, such as a third-party service breakdown or even a minor difference in load times across different regions, it can negatively impact your bottom line.


Best Practices for Load Testing Websites

While gearing up for load testing your website, it is crucial to keep in mind that you should try to simulate the most realistic situations. For that, you need to use a load testing platform like LoadView that offers real browser-based load testing with strategically placed geo-location servers for a comprehensive load testing solution. The following are some best practices for load testing:

  • Benchmark the performance of the CDN against your own server by performing load testing with and without your CDN provider. This will help you establish that your content delivery is faster, and accessibility is improved with CDN.
  • Test from different geo-locations with a well-distributed load according to your demand areas to analyze performance and network metrics. This will help you establish that your website is highly available around the world with the expected real-world load.
  • Monitor Cache status to analyze the content HIT/MISS/EXPIRED scenarios to optimize content caching strategy. Most user requests should experience a HIT with your CDN servers.
  • Load test HTTP/S to meet security and SLA requirements. This will also help you identify any mixed content issues that can result in an unsecured connection.
  • Load test all static resources to make sure that they are accessed properly without any breaking changes.


Load Testing Websites That Use CDNs: Conclusion

Utilizing CDNs to improve website and web application performance is a great way to ensure that your users get a consistent user experience, no matter where they’re located. Caching resources on edge servers located around the world minimizes the load requirements on the origin server, helping to decrease latency.  Try LoadView today and get up to 5 free load tests to get started. Or rather take a tour of the solution itself?  Sign up for a time with one of our performance engineers to walk through the LoadView platform and get all your questions answered.

Bonus Tip:  To make sure your website performs consistently and provide a seamless experience to your users continuously, monitor your websites and applications with the synthetic monitoring solutions from Dotcom-Monitor for a bird-eye view of your entire infrastructure. Synthetic monitoring tools emulate real-world user behavior and transactions using scripts. With the help of these tools, you can continuously monitor your web application, web pages, third-party services, etc from different geo-locations. This will help you proactively identify and resolve issues before they impact your end-user experience.