Almost any site can reap the benefits provided by rolling out a CDN, but generally the core reasons for implementing one are to offload bandwidth from your origin servers onto the CDN servers, and to reduce latency for geographically distributed users.
We'll go through these and several of the other major advantages afforded by using a CDN below.
If your user base is geographically dispersed, and a non-trivial portion of your traffic comes from a distant geographical area, a CDN can decrease latency by caching static assets on edge servers closer to your users. By reducing the distance between your users and static content, you can more quickly deliver content to your users and improve their experience by boosting page load speeds.
These benefits are compounded for websites serving primarily bandwidth-intensive video content, where high latencies and slow loading times more directly impact user experience and content engagement.
CDNs allow you to handle large traffic spikes and bursts by load balancing requests across a large, distributed network of edge servers. By offloading and caching static content on a delivery network, you can accommodate a larger number of simultaneous users with your existing infrastructure.
For websites using a single origin server, these large traffic spikes can often overwhelm the system, causing unplanned outages and downtime. Shifting traffic onto highly available and redundant CDN infrastructure, designed to handle variable levels of web traffic, can increase the availability of your assets and content.
As serving static content usually makes up the majority of your bandwidth usage, offloading these assets onto a content delivery network can drastically reduce your monthly infrastructure spend. In addition to reducing bandwidth costs, a CDN can decrease server costs by reducing load on the origin servers, enabling your existing infrastructure to scale. Finally, some CDN providers offer fixed-price monthly billing, allowing you to transform your variable monthly bandwidth usage into a stable, predictable recurring spend.
Another common use case for CDNs is DDoS attack mitigation. Many CDN providers include features to monitor and filter requests to edge servers. These services analyze web traffic for suspicious patterns, blocking malicious attack traffic while continuing to allow reputable user traffic through. CDN providers usually offer a variety of DDoS mitigation services, from common attack protection at the infrastructure level (OSI layers 3 and 4), to more advanced mitigation services and rate limiting.
In addition, most CDNs let you configure full SSL, so that you can encrypt traffic between the CDN and the end user, as well as traffic between the CDN and your origin servers, using either CDN-provided or custom SSL certificates.
If your bottleneck is CPU load on the origin server, and not bandwidth, a CDN may not be the most appropriate solution. In this case, local caching using popular caches such as NGINX or Varnish may significantly reduce load by serving assets from system memory.
A helpful tool to measure your page load speed and improve it is Google's PageSpeed Insights. Another helpful tool that provides a waterfall breakdown of request and response times as well as suggested optimizations is Pingdom.
A content delivery network can be a quick and effective solution for improving the scalability and availability of your web sites. By caching static assets on a geographically distributed network of optimized servers, you can greatly reduce page load times and latencies for end users. In addition, CDNs allow you to significantly reduce your bandwidth usage by absorbing user requests and responding from cache at the edge, thus lowering your bandwidth and infrastructure costs.
With plugins and third-party support for major frameworks like WordPress, Drupal, Django, and Ruby on Rails, as well as additional features like DDoS mitigation, full SSL, user monitoring, and asset compression, CDNs can be an impactful tool for securing and optimizing high-traffic web sites.source: digitalocean