&quot;Do one thing and do it well&quot; is problematic for things that store a lot of data. Especially for things that are supposed to be an authoritative source.<p>Getting storage right is very hard. Either it&#x27;s too low-level, and it&#x27;s hard for applications to coordinate complex operations without corrupting data; or you end up putting a lot of features in and end up with a SQL dbms; or everything does its own storage and you have a mess.