Thank you very much for your replies!
You have convinced me to use PostgreSQL with Ecto right now, because it is probably easier to start with and maintain, and having Mnesia’s distributiveness or the extra speed of an in-memory database is not of the most importance for this application (at least at this point in time).
What would be cool, though, is if there would be an Ecto<->Mnesia adapter at some point, because being completely independent from external services remains very compelling.
