True, of course.

And even a simple set like this brings in "distribution" issues for the app developper:

When do you connect ? When do you reconnect ?

Where do you get your connection credentials from ?

What should happen when those credentials have to change ?

Do you ever decide to connect to a backup db ?

Do you ever switch your application logic to a mode where you know the DB is down, but you still try to work without it anyway ?

Etc..

Those examples are specific to DBS, but in a distributed system any other services brings in the same questions.

With experience you get opinions and intuitions about how to attack each issues ; my question is still : "should you need to point a newcomer to some reference / book about those questions, where would you point to ?"