Wikipedia
CSQL
CSQL is an open source main memory high-performance relational database management system developed at sourceforge.net. It is designed to provide high performance for SQL queries and DML statements.
As there is no disk I/O, main memory databases provide a predictive response time (~10 microseconds for point lookup and ~20 microseconds for insert/update/delete operations) which is suited to real time and near real time applications. For more information see
It can transparently cache data from existing databases.
It can be configured to work as transparent, updateable, real time cache ( CSQL Cache ) for existing database management systems such as MySQL, and Postgres.