The creator of Elixir is in the Rails core team and helped (wrote?) write Rack. The creator of Phoenix built Rails apps for quite a while before finding Elixir—

The creator of Elixir is in the Rails core team and helped (wrote?) write Rack. The creator of Phoenix built Rails apps for quite a while before finding Elixir—their experience definitely helps because they take what is good about Rails but know which "pain points" to improve on.