Koa

Koa is a minimal, expressive web framework for Node.js created by the team behind Express, built around modern JavaScript features. Its middleware system uses async functions and an “onion” execution model, producing clean, sequential control flow for request/response handling. Koa keeps the core small and unopinionated—there’s no built-in router or templating—so developers compose only the pieces they need. The framework exposes a refined Context object to standardize request and response utilities without obscuring Node’s primitives. This design encourages readable middleware, robust error handling, and straightforward composition for tasks like authentication, logging, and body parsing. In production, Koa’s simplicity and async-first approach translate to predictable performance and maintainable server code.