At my current employer, we're working on a product that relies heavily on a graph DB (Titan, in this case). Performance characteristics vary dramatically based

At my current employer, we're working on a product that relies heavily on a graph DB (Titan, in this case). Performance characteristics vary dramatically based on the type of query you're trying to run so you have to be careful about how you use it. There are certain types of things you might do in a relational DB with no worries but that would perform horribly in Titan. The converse is also true, of course. For example, a query along the lines of "give me a list of friends of friends of person X" is very fast indeed on a graph database, whereas a query like "give me a random person" tend to perform horribly. But we've been able to get impressively fast, real-time performance on graphs with millions of vertices and tens of millions of edges. They're still niche products compared to NoSQL systems like Mongo, Redis, etc. But I don't see any reason to think think that Titan or Neo4J aren't production ready. Here's a good intro to Titan and how it works: http://www.slideshare.net/knowfrominfo/titan-big-graph-data-with-cassandra http://www.slideshare.net/knowfrominfo/titan-big-graph-data-...