Given that the \"Rails Way\" seems to be not to use foreign key constraints, I\'m looking for an alternative that will allow me to validate that the row a foreign key references
Simply use like below,
validates :user, presence: true
It will automatically check the existence of user record in db.
Reference from the Active Record Validation - presence:
If you want to be sure that an association is present, you'll need to test whether the associated object itself is present, and not the foreign key used to map the association. This way, it is not only checked that the foreign key is not empty but also that the referenced object exists.