names aren't namespaced and may not be strings (or arrays/hashes of strings). keys are strings (or ... of strings) and may be prefixed with a namespace. The transformation is done here: https://github.com/rails/rails/blob/7763cff2981757ab6a4d5796c1d17b98a2f57f0a/activesupport/lib/active_support/cache.rb#L509-L537