When to switch to a CDN?

Question

I have read about CDNs and what they do. The question I have is three fold.

1. When should you start to use a CDN? My site is small currently and do not see the need for a CDN but is there a general threshold that once crossed I should switch to a CDN? (Like say I have 2,000 visitors a day).

2. When you do switch to a CDN what should you put on the CDN? Just external JavaScript? All images? Some images? What are some general guides for what content goes onto the CDN and what should stay on your server?

3. Does use of a CDN affect SEO and how?

Answer 1

You shouldn't switch to a CDN too early. Read the update on hacked.com's experience with a CDN. If you don't have millions of visitors per day and your visitors are not distributed across a wide geography, then a CDN might slow your site down.

Instead, it would be wise to plan for using a CDN at some time in the future when designing your site, but not implementing it until needed.

When will the CND be needed: When two factors collide. Firstly that you tests show that the majority of users will see a speed improvement and secondly when it is financially viable for your site.

What to put on the CDN? Everything that doesn't change and is static. That means your database and server side code stays on your original site but all the other stuff like css, javascripts, images, videos and so on, go on the CDN. The CDN should also cache copies of your dynamic pages though how aggressive that cache should be depends on your site. Many CDN systems will automatically grab what contents they need without you doing to much. For example Google's new pagespeed CDN just needs you to point a cname in your dns and google will automatically pull the content as it needs it.

Answer 2

1) If your site has lot of text content and more media content then it is beneficial to host media content off your server. Few questions you should answer before switching to CDN - Is my content loading going to benefit from CDN ? If your site is simply wordpress based and updates less per day or week but is getting more traffic everyday then caching solutions like W3 Total Cache or WP-Super cache plugin helps for now. You can just host css and image files on CDN if it reaches 10k/day visits. But if you host lots of media content like videos, scripts, file manipulation scripts etc. then consider switching to CDN.

2) You should consider hosting media files - images, videos, javascript, flash. There are no fixed guidelines as every site and it's audience are different. You may benefit hosting javascript or other script files and images on CDN. In my personal opinion it is better to host text content on your own server and media content on external services like Amazon S3 or CDN services.

3) Google and Bing consider "loading time" as one minor ranking factor. This is the reason google launched page speed service recently. It'll not boost your ranking but if your site loads slow due to media content then it'll benefit from CDN and search engines will also push more weight to faster site. That's it. There is nothing more benefit or bias for CDN or page speed from search engines.