Starlette

Koa is a new web framework designed by the team behind Express, which aims to be a smaller, more expressive, and more robust foundation for web applications and APIs. By leveraging async functions, Koa allows you to ditch callbacks and greatly increase error handling. Koa does not bundle any middleware within its core, and it provides an elegant suite of methods that make writing servers fast and enjoyable. A Koa application is an object containing an array of middleware functions that are composed and executed in a stack-like manner upon request. Koa is similar to many other middleware systems that you may have encountered such as Ruby's Rack, Connect, and so on - however, a key design decision was made to provide high-level "sugar" at the otherwise low-level middleware layer. This improves interoperability, and robustness, and makes writing middleware much more enjoyable.