[pzaich]

I'm also in a similar position where I'd like to store approximately 560k records / user / year. My understanding is that Cassandra doesn't support some useful queries that would be useful when business logic is less clear (like group by)[1]. I'm leaning towards using PostgreSQL with a dedicated write DB until performance becomes an issue.

[1] http://stackoverflow.com/questions/17342176/max-distinct-and...