Size doesn’t always paint the right picture. A tank may win a war, but a bike will get you to your destination fast in a city!
Sinatra is a light weight / minimal Ruby web framework originally created by Blake Mizerany and currently maintained by Konstantin Haase. To be honest it is not entirely a framework but a domain-specific-language wrapping around Rack, the Ruby web server interface. Sinatra is a good suite for web-sites, small web applications (even APIs).
My first interaction with Sinatra dates nearly 6 years. Unlike many Rails developers, I started Ruby web-development using Sinatra.
Rails has a wide variety of in-built features and 3rd party plug-ins that just work with minimal configuration. It has a trade name “Rails Magic”. In the case of Sinatra, it involves a little more work, may be more than I like to emphasise.
My relationship with Sinatra remains and has always been complicated. I love its flexibility but some times Rails just works! That is why I decide on a per-project basis if to choose Sinatra or Rails.
Don’t get too confused. The technology stack, that is my responsibility, let me worry about it. All I need is the functional requirements.