title: Graph Database integration with Solr
body: <p>Are there any graph databases in production that are integrated with Solr?
  For example, I know Neo4j has Lucene integration but I'm not sure if you can build Solr on top of it yet.
  I believe AWS Neptune will but currently it is not in production so no definite answer.</p>
  
  <p>Any information would help!</p>