Enjoy the first edition in our series of 'Retailer's Guides', written by Managing Director Rob Smith. Make sure you also follow us on Twitter or sign up to our newsletter, so you don't miss our future editions!  

Over to Rob...  

A CDN is a Content Delivery Network, but what does that mean? How can it help a retailer? Do you need one? Where can you get one? All of this and more answered in this edition of 'Retailer's Guide'. 

Here’s the best way to explain what a CDN does. Under a normal situation, a website is housed on a number of servers. These servers respond to all of the visitor's requests, giving them the web pages themselves, the images, the styling instructions and so on. All of that gets smashed together by your web browser (e.g. Chrome) to form what you see.

As you can imagine, there’s a lot of repetition in here. The styling instructions rarely change visit to visit. That product image of the stuffed cat with the bow on it’s head will be the same for every visitor. As a result, getting your servers to constantly respond to the same request eats up a fair amount of their overall power and ability to cope with traffic. As your traffic grows, you really only want your servers doing the super important stuff. That’s things like processing payments, sending orders to your back office, registering new accounts and so on. You don’t want it doing trivial stuff like serving that cat image for the 50,000th time today.

Step forward the CDN...

The CDN sits in front of your website. It’s a gateway and a guardian to access your website, and takes care of a lot of the simple requests for you. How? It requests that cat image once from your server and then keeps a copy in it’s system, and keeps giving that to the website visitors' every time it’s requested. Every so often, it checks back to the server to see if it’s changed so it doesn’t get stuck with an old image either. Pretty simple stuff, no? The simplicity can save a tonne of server power. As a result, you need less servers for more traffic, allowing you to scale easier. CDNs are much cheaper than adding the equivalent server power.


Other benefits

Now you know how a CDN operates in it’s basic form, here’s a few more benefits:

1. International traffic gets a better experience
Generally CDNs have copies of your stuff on their systems all over the world. That means that when someone makes a request from Australia, instead of going all the way back to London to get the cat, it’s given to the user from somewhere in Sydney. Shorter trip, faster delivery.

2. Security
This is a big one in today’s world of hacking, DDoS attacks and all that jazz. As the CDN sits in front of your site, if it gets hit by an attack it often just blocks it straight off especially if it exhibits odd behaviour. Also, with DDoS attacks, where a lot of malicious traffic tries to take your website down, the CDNs have very sophisticated recognition and mitigate these quickly, so traffic often doesn’t get back to your servers to take them down. Clever stuff.

3. CDN bonuses
Certain CDNs also add extra features like optimising image sizes as they serve them. These vary from company to company.

Who are some of the main providers?

Akamai is the best known and longest standing one - and has a price tag to match. Cloudflare is one we use a lot at a variety of price points from Enterprise to the free solution depending on what a project needs. It’s done well for us so far and is very cost effective.


The conclusion here is that every site should be fronted by a CDN for speed, security and cost effectiveness. If you’re on a cloud-based commerce solution like Demandware, you’ve already got a CDN all built in and don’t need to worry about it. In Demandware’s case, that is Akamai.

Want to know more? Just drop us a line.