They are tools that solve different problems, imo. In CAP theorem[0] you have 3 groups of DBs. CA databases: SQL databases that are hard to scale ("partition")

They are tools that solve different problems, imo. In CAP theorem[0] you have 3 groups of DBs. CA databases: SQL databases that are hard to scale ("partition") but are always consistent and available. CP databases: MongoDB style databases that are consistent and partition tolerant, but trade availability (sometimes your queries will fail during high load). AP databases: CouchDB style databases. They are always available and are partition tolerant, but you may be querying stale data. [0]: https://en.wikipedia.org/wiki/CAP_theorem?wprov=sfla1 https://en.wikipedia.org/wiki/CAP_theorem?wprov=sfla1