(author here) It only uses Sinatra because I happened to know it and needed to bootstrap the low-level stuff. I don't know if it needs to be based on Sinatra in the long term - it should probably just use Rack.

Thanks for the reply. Interesting that you mention that it should just use Rack. It reminds me of a time a number of years ago where I was on a mission to use a framework which did not have a million and one dependencies, but just Rack.

Not sure you have come across https://github.com/Ramaze/innate (I am showing my age now :) . It is the core of the Ramaze framework. I really liked the philosophy of that project. Its a shame it never caught on though.

Roda would be worth considering for its routing tree architecture which can be more performant and maintainable than Sinatra's linear routing approach, especially as the application grows.