I tend to think of a classifieds site as pretty much the ideal case for a typical nosql approach... especially Mongo being a great fit. Today, I might use Post

I tend to think of a classifieds site as pretty much the ideal case for a typical nosql approach... especially Mongo being a great fit. Today, I might use PostgreSQL/Cockroach with some fixed and a JSON column for extra bits based on type of classified. Not everything fits into this mold, it's a matter of mix/match today, and there are no clear rules for how you get into scaling as needed...