I've never used Rails. I used Sinatra in the early days and over the last 8 years I've used Roda[0] and Sequel[1].

Our stack is front-end heavy with a very mature JS framework and the back-end is mostly an API server. Databases range from SQLite to Postgres.

Development is usually done on SQLite and staging / production on Postgres. Quite a few projects with SQLite DB in production as well.

[0]: https://roda.jeremyevans.net

[1]: https://sequel.jeremyevans.net

Sinatra is a great framework for fastly developing REST APIs. It benefits from almost the whole Rubygem possibilities while being fast to develop.

Middlemanapp is a great static website generator written in Ruby and easy to extend that I used many times to generate simple generated websites.

Jekyll is a great static blog generator.