[bestie]

Having the indirection there allows you to take the Rails features you want with your boundary clearly defining which ones you depend on.

You could start with Rails, get ActiveRecord querying, migrations and template rendering for free and then maybe swap it out for Sinatra and the Sequel gem (I have actually done this).

Knowing your where your dependencies and technical debts are is very empowering.

[binarysoul]

What does hexagonal mean?

[dcuthbertson]

It's a reference to Alistair Cockburn's "Ports and Adapters" pattern, also called "Hexagonal Architecture".[1] The only reason I ever heard of it is that it was mentioned in the book "Growing Object-Oriented Software, Guided by Tests", by Steve Freeman and Nat Pryce (a good book in my opinion).

[1] http://alistair.cockburn.us/Hexagonal+architecture