HttpClient Factory

Core Principles

1. Never new HttpClient() per request — Raw HttpClient creation causes socket exhaustion under load and ignores DNS changes. Use IHttpClientFactory to manage handler lifetimes.
2. Keyed clients over typed clients — Keyed DI (.AddAsKeyed()) 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. AddStandardResilienceHandler() provides sensible defaults in one line.
4. DelegatingHandlers for cross-cutting concerns — Auth tokens, correlation IDs, and logging belong in the handler pipeline, not scattered across service methods.

Patterns

Named Client with Resilience