org.janusgraph:janusgraph-inmemory (maven):  JanusGraph is a distributed graph database optimized for processing massive-scale graphs represented over a machine cluster. JanusGraph separates the concerns of graph processing and manipulation from storing the graph on disk, delegating that concern to an extensible set of persistence solutions. 
Keywords: bigtable|cassandra|elasticsearch|graph|graph-database|graphdb|gremlin|hbase|solr|tinkerpop