This discussion continues on. I think it is clear by now that the reason for choosing MySQL was due to the dependency cocktail skills of the team’s preference for Knex.js.
Because we also want that dependency too is not really a good reason to choose a database engine. That choice reveals priorities and limits on knowledge, in both my opinion and others’.
So, that’s why things are where they are. Ghost is still an awesome concept; the team just needs more support lower in the stack.