Mondrian is an OLAP (online analytical processing) engine written in Java. It reads from JDBC data sources, aggregates data in a memory cache, and implements the MDX language and the olap4j and XML/A APIs.
CSQL - suite of three products, embedded relational database / stand alone Main Memory Database / updateable bi-directional table level cache. All are exposed via standard SQL interfaces such as ODBC/JDBC.
ChaiDB is an embedded data storage developed at the kernel level by using B-Tree implementation. It is a natural database choice for name/value applications such as JSON. JSON-Cache utilizes ChaiDB to provide persistence and cache solution for JSON data.