FWIW, we were able to integrate Druid and Cassandra. Its only in PoC right now, but it seems like a powerful combination: http://brianoneill.blogspot.com/2013/05/cassandra-as-deep-storage-mechanism-for.html
-brian -- Brian ONeill Lead Architect, Health Market Science (http://healthmarketscience.com) mobile:215.588.6024 blog: http://brianoneill.blogspot.com/ twitter: @boneill42
