[tablespoon]

> Defining service boundaries and APIs with clarity around backwards compatibility is a good solution.

Can't you do that with one big database? Every application gets an account that only gives it access to what it needs. Treat database tables as APIs: if you want access to someone else's, you have to negotiate to get it, so it's known who uses what. You don't have to have one account with access to everything that everyone shares. You could

[sanderjd]

It would be easier to create different databases to achieve the same thing. Those could be in the same database server, but clear boundaries is the key.

[cerved]

Schemas can be useful in this regard

[Wicher]

Indeed! And functions with security definers can be useful here too. With those one can define a very strict and narrow API that way, with functions that write or query tables that users don't have any direct access to.

Look at it as an API written in DB functions, rather than in HTTP request handlers. One can even have neat API versioning through, indeed, the schema, and give different users (or application accounts) access to different (combinations of) APIs.

The rest is "just" a matter of organizational discipline, and a matter of teams to internalize externalities so that it doesn't devolve into a tragedy of the commons — a phenomenon that occurs in many shapes, not exclusively in shared databases; we can picture how it can happen for unfettered access to cloud resources just as easily.

But here's the common difference: through the cloud, there's clear accounting per IOP, per TB, per CPU hour, so incentive to use resources efficiently is can be applied on a per-team basis — often through budgeting. "Explain to me why your team uses 100x more resources than this other team" / "Explain to me why your team's usage has increased 10-fold in three months".

Yet there's no reason to think that you can only get accounting for cloud stuff. You could have usage accounting on your shared DB. Does anyone here have experience with any kind of usage accounting system for, say, PostgreSQL?

[sanderjd]

I think we're getting hung up on database server vs. database as conceptual entity. I think separation between the entities is more important (organizationally) and don't think it matters as much whether or not the server is shared.