.NET 9 Middleware Pipeline: Advanced Patterns and Performance 🚀

TL;DR — The ASP.NET Core middleware pipeline is where your app does its real work, but most developers only scratch the surface. In .NET 9, you've got new tools like MapStaticAssets , better exception handling, and the same old performance patterns still apply: short-circuit early, order cheap before expensive, and never sync-over-async. Let's look at the patterns actually worth knowing. Pipeline Basics Here's the mental model that actually helps: your middleware pipeline is a series of functions. Every incoming HTTP request flows through them in order. Each one can: Do some work Decide whether to pass the request downstream Short-circuit and return immediately You wire it up with three extension methods: Use — does work, then calls next() to continue down the pipeline Map — forks the pipeline based on a URL path Run — terminal. No next() . The pipeline ends here. var builder = WebApplication . CreateBuilder ( args ); var app = builder . Build (); // 1. Use — passes through to next mid