Middleware pipeline, DI lifetimes, configuration and options, minimal APIs, and hosting.
3 questions in .NET & C#.
Detached ASP.NET Core background work can fail after the response because the request scope is disposed. Copy required values, create a fresh service scope, and run tracked work through IHostedService, BackgroundService or a durable queue.
ASP.NET Core DI lifetimes matter because a singleton that captures a scoped service turns per-request state into process-wide state. Captive dependencies cause stale data, threading bugs and disposed object failures.
The pipeline is an ordered list you assembled, and authorisation cannot decide anything before routing has selected an endpoint to decide about. Registered in the wrong order it either runs against nothing or never runs at all, and neither produces an error - the request simply succeeds.