> "MongoDB, Cassandra, Redis, or Hadoop" Adding Hadoop in the mix tells me he doesn't know what a NoSQL is.
Of course we can bikeshed all day and split hairs about the precise definitions, but in the spirit of pragmatism, I would absolutely put "Hadoop" as a form of NoSQL storage solution. In fact, I'd say the most distinct of the items mentioned is Redis, and Redis is the tool from this list that has use cases that tend to differ the most significantly from traditional RDBMSs (I'm thinking specifically cases where Redis is used as a buffering layer to help relieve congestion for a highly visited base data store). But even so, I still don't think it represents any sort of taxonomic error to put them all in the NoSQL category, at least for practical purposes.