Neo4j is a NoSQL graph database. Like its cousin, MongoDB, Neo4j uses the document structure for storing records. Where it differs is in its use of the graph model. Relationships between records are stored in Neo4j as the vector between two documents or nodes. This means that relationships can be traversed at very little computational cost, so friends of friends of friends for example can be found in an instant where other databases would find themselves backed up by a recurring query.