ScubaDev

Neo4j + RDF/SPARQL extensions

Rexter + Titan

AllegroGraph 2 Use

Neo4j 2 Use

G.C.H.Q Gaffer 2 Use

Virtuoso 2 Use

Memcached

Elastic Search

MySQL

Zero MQ

CockRoachDB

CouchBase

RabbitMQ

Redis (cache)

RethinkDB (documents)

PostgreSQL (sql)

MongoDB (documents)