The documentation doesn't seem to specify which cache backends are supported/required.
In the section about using Redis for flush lists, it says:

When using Redis, memcached is still used for caching model objects, i.e., only the flush lists are stored in Redis. You still need to configure CACHES the way you would normally for Cache Machine.

So does that mean memcached is always required? Or is this part of the documentation outdated/misleading?