The databases of today are in many cases built for specific purposes. Some of the more common ones we see every day are relational databases, document-oriented databases, Operational databases, Triplestore, and Column-oriented databases / c-store. Typically relational, document-oriented, operational, and triplestore databases are used to solve frontend database problems. Then you have databases that are column-oriented or similar that focus on solving warehousing and backend database problems. These products don’t need to solve those problems, though they are often best suited for them.