Windows Azure supports the elastic provision of web and application services. The number of role instances used to provide these services can be varied to match the current demand for them. Furthermore, the instances of a web role are located behind a load balancer that forwards traffic to them using a round-robin algorithm.
The load balancer does not support session stickiness, which can cause problems when session state is used on a web role. Each web page provided to the user may come from a different instance of the web role, so some means must be provided so that all the instances can access the same session state. In the context of a web role, obvious choices for the session state store are Windows Azure tables or SQL Azure. However, neither of these provide for the local caching of data.
The Windows Azure AppFabric Caching Service is a Windows Azure-hosted version of the Windows Server AppFabric Caching Service ...