Beginners Guide to CDNs
What is it?
Beginners Guide to CDNs
What is it?
A CDN or Content Delivery Network is an interconnected series of edge servers that sends cached content to users, making delivery of your website assets to them much faster. Without a CDN, your website content would use one or maybe a small handful of servers to deliver your content to users. This means that if a user is in Sydney, Australia and your closest server to them is in San Francisco, California (a distance of 4.5k miles), the user will have a much greater wait time to receive your website assets than is necessary. A CDN operates by using edge servers or Points of Presence (PoPs) at many locations around the world.
How does it work?
As mentioned above, a CDN is primarily used to mitigate latency when a user requests your website. When someone makes a request, the nearest PoP will be queried for your website assets. If someone has already requested your website from that particular PoP then the data will already be cached there (provided the time-to-live (TTL) hasn’t yet elapsed). If a user is the first to request your website from a specific PoP or the TTL is exceeded, then the request for your site will be forwarded on to the origin server (the main server that hosts your website assets).
Another advantage of using a CDN is that it decreases load on your origin server. When a CDN is caching your content in edge servers, your main server that provides content, the origin server, is not hit as often. It’s only pinged when a PoP either doesn’t have your content or when the TTL has elapsed on that content and its become stale. This can increase uptime for your origin server and mitigate DDoS (distributed denial of service) attacks.
How can I set up a CDN?
There are many CDN providers you can work with such as Vercel, Cloudflare, AWS, and more. These tools already have robust PoPs established and have built the infrastructure for you to easily hook into their CDN network for your project. With a platform like Vercel, it’s as easy as connecting your Github project and the rest will be taken care of for you automatically.
What content is best for a CDN?
CDNs hold cached content that will be retrieved for anyone visiting your site. As this is the case, personalized data or anything that needs realtime freshness will not be a good fit. CDNs are great for things like static content and images that can be served to everyone and don’t change incredibly frequently. Think of a marketing page holding your branding content and images which will be the same for anyone visiting your page. Even something like a blog can be served from a CDN. That data will change as new blog posts are made but many platforms and frameworks will allow you to specify a TTL for content cached on a CDN so there is some cadence where new content is fetched.
CDNs are a crucial piece of infrastructure if you have more than a highly localized audience. The speed they provide will keep users on your page and help ensure they’re return to your content again and again, especially when combined with other optimizations such as passing Core Web Vitals scores, user-first design, and fast APIs.
Additional Resources
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