I don't claim that it is easy, especially with an RDBMS. Actually, given the few courses I took in university on database design, I know its very non-trivial.

I don't claim that it is easy, especially with an RDBMS. Actually, given the few courses I took in university on database design, I know its very non-trivial. But MongoDB is not an RDBMS. There are no joins, so a query can only touch one collection (table) at a time anyways, so at least in that regards its much easier than an RDBMS.