A website has to be fast, or it will lose users. When it uses files from a distant part of the world, or from a slow server, it slows down its own delivery, and people will give up before the page loads. A CDN (Content Delivery Network) with a good caching service can protect your site from this risk.
Our Web browsers use caching all the time. Once the browser loads an image from the server, it doesn’t have to load it again to reuse it. If the same logo appears on every page of a site, the computer only has to get it once. CDN caching takes this idea to the next level, holding resources on a server that’s fast and close to your site’s server, so that any users fetching them get a speed benefit the very first time they fetch the resources.
A really effective CDN performs multiple levels of caching. Besides the relatively small, fast “edge servers” which are close to the client servers, a middle tier of cache servers with larger capacity feeds them.
Caching follows expiration rules. Some resources are volatile and shouldn’t be cached; the server will tell the cache when this is the case, the same way it tells your browser’s cache. Sometimes, though, contents change unexpectedly. When this happens on your personal computer, you can tell it to clear the cache so that misbehaving pages will start working again. A robust CDN provides its managers with the same capability. Generally a CDN will be conservative in how long it retains cached resources, since changes are harder to notice and affect more people than ones cached in a browser.
For more information about our caching and content acceleration offerings, please contact us.