With AEM as a Cloud Service, Adobe has solved some extremely challenging problems in order to make AEM scale in the cloud. These challenges relate to the underlying implementation and concepts behind AEM and are: Each AEM instance stores the application code in the repository which is, therefore, mutable Each AEM instance stores the content repository on the filesystem Publishing content from an author to publisher instances is not journaled and therefore cannot be reproduced on new instances How did Adobe overcome these challenges? And what's so different between AEM as a Cloud Service's approach from AEM "Classic"? As I discussed in my previous blog post dissecting the bundles in AEM as a Cloud Service, AEM "Classic" and AEM as a Cloud Service share most of the same underlying technologies. The key difference is how two tools use these technologies. There are some key differences which enable Adobe to dynamically scale AEM as a Cloud Service, vs the fixed model for AEM "Classic".