No magic, no unicorns, just simply create your simple paths and get your web app or simple API done.
If what you are looking for is a simple, yet elegant solution, but Rails is way too much, then Sinatra is for you.
Remember, it is for simple web services or web pages, but if you are scaling your Sinatra app for running daemons, many asynchronous jobs, complex UI, etc. Then, Sinatra might not be a good fit.
It was made for simple API services with none-complex database operations, anything bigger than that might require specialized software.
Do not go with the first Blockchain, complex MVC-based, RX-based or any other crazy architecture when what you are trying to solve is a simple problem, simple problems require simple solutions.
Sinatra is easy and powerful enough to get your quick API shipped with no harm.
Simple APIs have been made with Sinatra like a charm, no need for a complex Ruby on Rails application for a simple web service, developers just love it.
Sinatra is a great framework for those who already know Rails but want to do a simple API or single page application.
The lack of useful methods that Rails provides. But I think it's by design. If you want to use something more just use Rails or install parts of it like active support.
In case you're looking for a small library to build API's you're on the right path.
I designed an internal API, my goal was to deliver a Proof of Concept to my director in order to work full time on the project. Sinatra helped me to do it really quickly and after that I got the time to work on my project (and it is still running Sinatra!).
If you need something that is lighter than Rails but more full-featured than Rack, Sinatra is a excellent choice.
I dislike the lack of community adoption - there aren't a lot of libraries and whatnot built on-top of Sinatra beyond normal Ruby libraries.
If you're looking for a lightweight web framework for Ruby, use Sinatra.
We use Sinatra for a little in-house application that handles reports and dashboards. Sinatra is light and easy to work with, and I've had inexperienced people do work on it as well.
Sinatra is very simple to get started with using even script style Ruby and a variety of template renderer plugins, but can easily grow with your requirements combined with Rack middleware and any Rack webserver.
The DSL isn't particularly well suited for defining API routes, however this can be solved by combining Sinatra with Grape or defining custom helpers.
Sinatra's main offering is giving you a powerful URL building / matching interface, so that you can start serving up whatever you need, be it an API or a web application.
I use it with Ruby, and creating a web app is relatively easy once you know how to structure the app itself.
Should you encounter any errors, Sinatra is usually fairly clear telling you what's wrong and in which point, which is definitely not common to development platforms.
Initially it can be puzzling to remember how to structure the app, and what goes where...
I'm relatively easily creating web apps starting from Ruby programs
Sinatra doesn't have high barriers of entry for both beginners and those more experienced who want to build out a ruby app without requiring all the additional extras included in bigger frameworks like Rails.
It is what it is - which is pretty basic and no frills. If you go into using that with that in mind there won't be surprises when you can't extend it out.
Great for beginners to play around with smaller apps and enhance their ability to create routes and get comfortable in a smaller environment.