WebSphere eXtreme Scale provides huge memory stores on commodity hardware. What can't you do with large, cheap memory stores?
These memory stores are distributed and incorporate redundancy to be highly available.
Data in memory is much quicker and easier to access than memory on disk. End user response times and system throughput are improved. Load on backend EIS and databases are reduced by large memory caches, thus increasing the workload you may process and your scalability.