HttpClient Factory Core Principles 1. Never per request — Raw creation causes socket exhaustion under load and ignores DNS changes. Use to manage handler lifetimes. 2. Keyed clients over typed clients — Keyed DI ( ) is the recommended pattern in .NET 10. Typed clients captured in singletons silently break handler rotation. 3. Resilience is not optional — Every external HTTP call needs retry, circuit breaker, and timeout. provides sensible defaults in one line. 4. DelegatingHandlers for cross-cutting concerns — Auth tokens, correlation IDs, and logging belong in the handler pipeline, not scatt…