Basically:
Foo.where(attributes).first_or_create
Is the same as:
Foo.find_or_create_by(attributes)
#first_or_create is sometimes misunderstood as people expect it to search by the attributes given, but that is not the case. Aka
Foo.first_or_create(attributes)
Will not search for a foo that satisfies the attributes. It will take the first foo if any are present. It’s useful if the conditions for finding are a subset of those used for creation. Aka
Foo.where(something: value).first_or_create(attributes)
Will find the first foo where something: value. If none is present, it will use attributes to create it.