Weighing the Benefits of a CDN

A content delivery network, or CDN, can be a powerful way to boost the performance of cloud-based workloads. But CDNs also increase your cloud costs and add complexity to your workflows. That’s why it’s important to ensure that the benefits of a CDN outweigh the costs before signing up for CDN services.

What Is a CDN?

A CDN is a network of servers that host cached copies of website or web application content. The servers are typically dispersed across a geographic area, with each server delivering content to users closest to it. In this way, CDNs reduce the amount of time it takes for content to reach users.

Benefits of a CDN

By reducing the geographic distance between your users and your content, CDNs can boost site load times. That is the primary advantage of a CDN.

The benefits of a CDN also include an increase in site reliability because traffic can be rerouted to a different server in the CDN network in the event that one server fails. CDNs provide the security benefit of helping to resist DDoS attacks as well as ensuring that an attack directed at a single server will not bring down your entire application.

Drawbacks of a CDN

The two main disadvantages of a CDN, as noted above, are cost and management overhead.

Unless you have the resources to build your own CDN from scratch (which is not practical for all but the largest companies), you have to pay a CDN provider to distribute your content on a CDN. That can increase your overall cloud spend significantly, depending on how much content you host on the CDN and how many user requests the CDN serves.

You also have to configure your content to be hosted on a CDN, which takes time. And if you use a CDN, it becomes one more thing you have to monitor and factor into application testing (because CDNs can impact application performance). In all of these ways, CDNs increase the burden placed on IT teams.

Do You Need a CDN?

Just because CDNs are one way to boost performance, reliability and security doesn’t mean that they are the only way and best way to achieve these things.

Before deploying your application to a CDN, ask yourself these questions.

How fast and reliable is my site currently?

The first question to consider is how well your site is performing, and how reliable it is, without a CDN. If your pages are already loading for most users in less than 1 second, you probably won’t gain much of a performance boost from a CDN. If you experience minimal downtime, a CDN won’t help much on that front, either.

Are my users geographically dispersed?

CDNs can substantially improve page load time for users who are distant from your main application servers. But if your users are all (or mostly) in the same geographic region, you don’t need a CDN to optimize their experience.

Instead, simply host your application in a data center that is located in that region, which will be cheaper and easier than using a CDN.

What are my biggest performance pain points?

Even if your users are geographically distributed, you should assess whether their location is a key limitation in your application’s or website’s performance. If it’s not, do some testing to determine what the biggest pain points are and to determine which methods will do the most to help you optimize performance.

You may discover, for example, that simply compressing more of lazy loading, or making better use of client-side scripting, could have a greater positive impact on performance than using a CDN.

How much control do I need over content?

Using a CDN service means hosting your content on infrastructure controlled by a CDN provider. While there is nothing inherently insecure or problematic about doing this, it could be an issue for organizations that need rigid control over who has access to their data and where the data is stored.

CDNs also may not work for organizations that face tight data sovereignty requirements because it’s not always possible to limit your CDN content to servers located in specific jurisdictions.

How easily will my hosting architecture work with a CDN?

The amount of effort required to deploy content to a CDN can vary quite a bit depending on how your application or website is hosted.

If you are running everything in a single public cloud, integrating it with the CDN service offered by your cloud host will typically be relatively simple. But if you are hosting your workloads in a private data center, or they are spread across multiple clouds, it may be more complex not only to get your content into a CDN, but also to extend your application delivery pipelines in such a way that updates will be pushed to the CDN automatically whenever you modify your sites or apps.

Conclusion: A CDN Sometimes Makes Sense

CDNs are a great resource when you have a large, geographically distributed user base and you are failing to optimize their experience using conventional, centralized hosting infrastructure. Indeed, the benefits of a CDN outweigh the drawbacks for many companies. But, in other cases, there may be lower-hanging fruit that will enable you to achieve a better performance and reliability boost at a lesser cost than using a CDN.