Middleware : overview : remember

Summary

Middleware is the code that sits between inputs and handlers, forming a pipeline that processes requests and responses. It handles cross-cutting concerns like authentication, logging, validation, caching, rate limiting, and error handling. Ordering and short-circuiting are key; each unit can mutate context, call next, or stop early. Common across Express, Django, ASP.NET, and Koa. Benefits include reuse and separation of concerns; risks include latency and hidden coupling. Prefer small, composable, testable pieces with explicit contracts and measured impact.