koa

Koa is a lightweight web framework for Node.js created by the same team behind Express. It was designed to be a smaller, more expressive, and more robust foundation for web applications and APIs by leveraging async/await instead of callbacks. Koa does not bundle any middleware within its core, instead providing an elegant suite of methods for writing servers with a cascading middleware architecture that uses async functions natively. The context object (ctx) in Koa encapsulates both the request and response into a single object, providing helpful shortcuts for common operations. Koa's middleware stack executes in a downstream-then-upstream pattern, which makes it intuitive to implement cross-cutting concerns like error handling, logging, and response timing. The framework is significantly smaller than Express and gives developers more control over what gets included. Koa is particularly well-suited for developers who want Express-like simplicity but with modern async/await patterns and a cleaner, more composable middleware system.