Most cache products used Map-based APIs to store data as key-value pairs. The ObjectMap API and the dynamic cache in WebSphere® Application Server, among others, use this approach. Though successful, the Map-based APIs have some limitations.
The EntityManager API uses the existing Map-based infrastructure, but it converts entity objects to and from tuples before storing or reading them from the Map. An entity object is transformed into a key tuple and a value tuple, which are then stored as key-value pairs. A tuple is an array of primitive attributes.
This set of APIs significantly eases the use of eXtreme Scale by following the Plain Old Java Object (POJO) style of programming that is adopted by most frameworks.