I serve many, many millions of rows, collect real-time statistics, push real-time updates, and maintain data integrity and consistency... all from a single database server. If our workloads require it we're prepared to scale out horizontally. I'm really looking forward to PostgreSQL 10's new parallel query features for some of our analytics work. Stack Overflow runs everything across what, 4 MS SQL Servers in total?…
Exactly! How about "developers have failed the databases" The majority of the developers don't use (or don't know how to) views/stored procedures/roles/triggers. Whenever you mention something like this you hear "omg, you put business logic in the db? everybody knows that does not scale" or "we deconstruct our request into a few simple queries instead of a join so we run super optimal"
Showing a consistent interface for data update and query.
When there are multiple teams developing against the same DB server, they might be able to see most or all of the tables, but they each might implement updates/selects (SQL queries) that exhibit extremely different results - which either present or update the data in potentially incompatible or inconsistent ways.
This ultimately manifests itself as errors/bugs which can be very difficult to figure out what went wrong where and why (and correcting the data becomes a nightmare).
Things get even worse when you have people querying the data via ad-hoc methods (like ODBC to an Excel file or something weird like that). Essentially, it is possible (likely) that every team sees a slightly (or greatly) different view from each other.
Coupling the BL closer to the DB level would prevent this; whether via the tools mentioned (views, triggers, etc) or something else. Ultimately, app developers shouldn't be hitting the DB tables directly, but going through these interfaces.
Of course - that brings up a host of problems on its own (table updates become an issue of coordination and conflict between teams, etc) - and there's also the issue of implementing versioning of the business logic (and how that relates to current/past DB structure)...
...but implementing it would solve a lot of headaches (and create more I guess).
/sigh