Agreed. Erlang's maps have two different operators when setting values on them, one if you care that the key already existed and one if you don't, so in that wa

Agreed. Erlang's maps have two different operators when setting values on them, one if you care that the key already existed and one if you don't, so in that way you can still somewhat enforce strictness of keys. But you can relax that strictness when it comes time to roll out changes.