WebSphere eXtreme Scale provides an extensible framework to simplify the caching of data used by an application. It can be used to build a highly scalable, fault tolerant data grid with nearly unlimited horizontal scaling capabilities. WebSphere eXtreme Scale creates infrastructure with the ability to deal with extreme levels of data processing and performance. When the data and resulting transactions experience incremental or exponential growth, the business performance does not suffer because the grid is easily extended by adding additional capacity in the form of Java virtual machines and hardware.
Simple .. it is an centralized and flexible caching grid.
To make it easy.. lets think this way. you have websphere application server network deployment installed. your application is expecting more users, what would you do? Check system resources and add another JVM or you will add another node to that cell. You can extend your eXtreme scale also in the same way.. hence it is flexible.
how is it fault tolerant?
eXtreme scale has two important comonents, Catalogue server(CAS) and Container server(COS). you generally use multiple CAS and COS. The product is designed in way that if any of these components fails .. it will readjust/reconfigure itself to minimize the effect and work with available servers. We will learn more about this in the next parts of this series about each failure scenario.