Fiery is a lightweight and flexible framework for web servers build on top of the httpuv package. The framework is largely event-based, letting the developer attach handlers to life-cycle events as well as defining and triggering their own events. This approach to development is common in JavaScript, but might feel foreign to R developers. Thankfully it is a rather simple concept that should be easy to gradually begin to use to greater and greater effect.
Fire for the main approach to build your server logic