> The API failed silently because the database connection pool was exhausted downstream.

I work with a team that does stuff like this, returning a 200 and a body containing "error: I didn't do what you said because _insert error here_"

The problem is that you returned OK instead of ERROR when things were not OK and there was an ERROR.

Its a design that smells of teams trying to hit some kind of internal metrics by slightly deceptive means.