Neo4j is probably the most popular graph database. It is developed by Neo4j, and it is a native graph database: Neo4j is built from the ground up to be a graph database. It’s the product of the company Neo Technology, with the Community Edition under the GPL license. For highly available and scalable Neo4j Clusters, you need the Enterprise Edition. Neo4j is ACID compliant. It’s Java-based, but has bindings for other languages, including Ruby and Python.

Neo4j supports its own Cypher query language, as well as Gremlin. Cypher supports advanced graph analytical queries such as transitive closure, shortest path, and PageRank.