Is it necessary to start a middle manager for tasks?

Is it necessary to start a middle manager node if I am submitting tasks? Can overlord take care of that?

I was reading http://druid.io/docs/0.6.146/Production-Cluster-Configuration.html when I saw that middle manager is being used separately.

Hi Aseem, an overlord can run in local mode to run tasks. The production configuration was taken from a cluster with around 40 trillion raw events and ingesting over 1M events/s, so in that case, the indexing service needs to run in distributed mode.