Purpose of namespace option

[collimarco]

I see that in the default config/cache.yml and in the readme there is this option:

namespace: <%= Rails.env %>

What is its purpose?

If I understand correctly, it just prefixes every cache key (key column in Solid Cache) with production/ (or development/, etc.)... but why?

It seems redundant to me, since every environment uses a different database (obviously). It also adds unnecessary size to the table and to the indexes.