If DB works beautifully, it should not be a problem. But in reality it doesn't. Also DB doesn't live in vacuum, so you are facing these challenges: * ORM bypas

If DB works beautifully, it should not be a problem. But in reality it doesn't. Also DB doesn't live in vacuum, so you are facing these challenges: * ORM bypass, for better performance. * Sharding and application level handling of sharding (making DB not transparent) * Replication (and obviously, delays) And there are always tons of application level code just written because DB just cannot do it efficiently.