Optimizing your HttpClient usage - Nico Vermeir - NDC London 2026

In this NDC London 2026 talk, Nico Vermeir, a Cloud Solution Architect at Microsoft, provides a comprehensive deep dive into optimizing HttpClient usage in .NET. He begins by explaining the importance of HttpClient in modern applications and the common pitfalls developers face. The talk covers the internal workings of HTTP calls, including DNS resolution, TCP handshake, and TLS handshake, emphasizing the cost of creating new HttpClient instances. He demonstrates the negative impact of disposing HttpClient in a using block, leading to socket exhaustion. The solution is to use IHttpClientFactory, which manages a pool of HttpMessageHandlers, allowing short-lived clients without the overhead of re-establishing connections. Vermeir shows how to configure named and typed clients, set base addresses, and handle errors properly using EnsureSuccessStatusCode and try-catch blocks. He also introduces delegating handlers for intercepting requests and responses, enabling cross-cutting concerns like logging or circuit breakers. The talk concludes with practical advice on connection lifetime, DNS updates, and avoiding shared cookie containers. Overall, the session provides actionable best practices for improving performance and reliability in .NET applications.