When WebSphere® eXtreme Scale is used as a side cache, the back end is used with the data grid.
You can configure the product as a side cache for the data access layer of an application. In this scenario, WebSphere eXtreme Scale is used to temporarily store objects that would normally be retrieved from a back-end database. Applications check to see if the data grid contains the data. If the data is in the data grid, the data is returned to the caller. If the data does not exist, the data is retrieved from the back-end database. The data is then inserted into the data grid so that the next request can use the cached copy. The following diagram illustrates how WebSphere eXtreme Scale can be used as a side-cache with an arbitrary data access layer such as OpenJPA or Hibernate.
Side cache plug-ins for Hibernate and OpenJPA