OrientDB is an Open Source Multi-Model NoSQL DBMS with a native Graph Database engine. Written in Java, it is incredibly fast: it can store up to 150,000 records per second on common hardware. Even for a Document based database, the relationships are managed as in Graph Databases with direct connections among records. You can traverse parts of or entire trees and graphs of records in a few milliseconds. Supports schema-less, schema-full and schema-mixed modes. Has a strong security profiling system based on user and roles and supports SQL amongst the query languages. Thanks to the SQL layer, it's straightforward to use for those skilled in the relational database world.