Neo4j

Summary
- It seems like Neo4j is helpful for making join-heavy queries orders-of-magnitude faster.
Links
- http://stackoverflow.com/questions/19570654/do-graph-databases-deprecate-relational-databases
- https://groups.google.com/forum/#!topic/neo4j/mts6H9Py-2I
- https://neo4j.com/developer/graph-db-vs-rdbms/
  - "If you use many-to-many relationships, you have to introduce a JOIN table (or junction table) that holds foreign keys of both participating tables which further increases join operation costs. Those costly join operations are usually addressed by denormalising data to reduce the number of joins necessary."
  - "This ability of pre-materializing relationships into database structures allows Neo4j to provide performances of several orders of magnitude, especially for join heavy queries, the minutes to milliseconds advantage that many users leverage."