Rails in 2010 was just coming around to adopting foreign keys, and the rubygem Foreigner made it happen before it was a proper rails feature. The idea of rails

Rails in 2010 was just coming around to adopting foreign keys, and the rubygem Foreigner made it happen before it was a proper rails feature. The idea of rails enforcing unique constraints and FKs back then was... Optimistic. The design constraints assumed exactly one rails instance would access the database at any given time to ensure consistency. Not a great assumption.