WebSphere eXtreme Scale is all about cache, but what cache?

Spare cache - only keeps a subset of the data
Complete cache - keeps all the data
Side cache - provide read and query performance as a temparory storage in parallel to the database. This is better than the regular cache because it has automatically replication capability between all processes
In-line cache - works between the application and the database through a backend load plug-in. In-line allows the application using WXS API to do
a. read through
b. write through
c. write behind