MonetDB is an open source high-performance database system developed at CWI, the Institute for Mathematics and Computer Science Research of The Netherlands. It was designed to provide high performance on complex queries against large databases, e.g. combining tables with hundreds of columns and multi-million rows. As such, MonetDB can be used in application areas that because of performance issues are no-go areas for using traditional database technology in a real-time manner. MonetDB has been successfully applied in high-performance applications for data mining, OLAP, GIS, XML Query, text and multimedia retrieval.

MonetDB achieves this goal using innovations at all layers of a DBMS: a storage model based on vertical fragmentation, a modern CPU-tuned vectorized query execution architecture that often gives MonetDB a more than 10-fold raw speed advantage on the same algorithm over a typical interpreter-based RDBMS. MonetDB is one of the first database systems to focus its query optimization effort on exploiting CPU caches. MonetDB also features automatic and self-tuning indexes, run-time query optimization, a modular software architecture, etcetera.