A graph database is similar, only it uses direct-record-ids for linking connected entities and not indexes. So instead of doing joins on indexes it follows rec

A graph database is similar, only it uses direct-record-ids for linking connected entities and not indexes. So instead of doing joins on indexes it follows record-pointers during graph traversals. In the graph databases book (graphdatabases.com) there is a chapter on the internal architecture of Neo4j.