Reddit uses Cassandra for a very small part of their functionality - their primary database is Postgre. Digg has yet to transitation over to Cassandra and gener

Reddit uses Cassandra for a very small part of their functionality - their primary database is Postgre. Digg has yet to transitation over to Cassandra and generally, their transition has been delayed (even if they have a lot more resources than a regular startup). Facebook only uses Cassandra for inbox search, their primary database is MySQL. The bottom line is to use NoSQL where it makes sense and where it solves the job better than relational databases.