Working with rails caching

Rails.cache.write('name','Hello this is string' , :expires_in => 1.week)
Rails.cache.read('name')

i use these syntax but always it's nil
=> nil

What does Rails.cache.class return?

There are different caching backends. If you're using NullStore or if the backend service is not available (server not running) Rails will not complain, but it'll produce the results you're seeeing.