Yes, the word "constraint" is confusingly absent (or, rather, used colloquially) in the OP. > FKs impose a lot of constraints on what's possible and what's not

Yes, the word "constraint" is confusingly absent (or, rather, used colloquially) in the OP. > FKs impose a lot of constraints on what's possible and what's not possible. Thanks again for the further clarification.