[djur]

Phoenix is much closer to Rails in terms of its goals than it is to Sinatra. It's a full-featured framework with asset handling, a recommended file layout, template discovery and compilation, generators, etc.

As far as I can tell, most projects one might use Sinatra for are done in Elixir by just working with Plug directly (Plug being the Elixir analogue to Ruby's Rack). I'm sure there are many lightweight web frameworks for Elixir out there, but I haven't seen any with Sinatra's level of ubiquity.