You will likely be happy with PostgreSQL or MySQL. If you don't know why you're not using a SQL database, likely you should be. If you do want to experiment w

You will likely be happy with PostgreSQL or MySQL. If you don't know why you're not using a SQL database, likely you should be. If you do want to experiment with NoSQL databases, MongoDB is probably the easiest to get going with (which is why it is so widely used). However, you seem statistically unlikely to be in the group that is happy with MongoDB in production :-) HBase has a much brighter future for the NoSQL use cases (and is even getting SQL support!)