...
AEM 6.x with Apache Sling uses TarMK with Apache Jackrabbit Oak. Key aspect of speed is the combination deserializes the repository into memory. It is not caching the repository in memory. The repository exists in memory and uses the tar files to serialize adn persist the data. It will deserialize the entire repository into memory if enough memory available. So give AEM lots of memory.
...
Setup of Web Server Dispatcher
Install Apache Web Server.
Load the module..
Setup of AEM Application Server
...