Content distribution for worldwide audience is not a trivial task. Most of the time the goal is very well known - keep your users happy and deliver them content they need as fast as you can.
There are at least two ways you can achieve that. You can build (and manage!) your own solution (AEM/dispatcher farms spread across the globe) or put a CDN in front of your application stack. The first one may sound tempting, but on second thought you quickly realize it's too much hassle and you would rather go for CDN. Regardless of the solution a set of problems stays the same.
Back in the old days you could just cache (almost) everything, as your website was pretty much static, but currently it's much more complicated. Your AEM stack is built from dynamic components that fetch data from 3rd party apps, there's a search engine under the hood and all crucial content is available for logged-in users only. To be even worse your resources are updated multiple times a day. Is it even possible to leverage CDN for that type of websites?
Have you ever tried to cache customized content that is available for authenticated users? Or authorize them at the edge? Or maybe you were crazy enough to implement CDN, not only for content served from AEM publish, but also in front of your authoring? In my talk I'd like to present you how we integrated AEM app that serves content to users distributed all over the world with heavily customizable content delivery network (Fastly).