You've deployed your fifth microservice. Requests flow through an API gateway, hit an order service, fan out to inventory and payment, and eventually land in a notification pipeline. Everything works — until it doesn't. A customer reports that checkout takes 12 seconds. Your logs show nothing unusual. Your metrics say average latency is fine. But somewhere in that chain of services, something is dragging, and you have no idea where. This is the observability gap that kills microservice architectures. Monoliths gave us stack traces. Microservices gave us distributed amnesia. OpenTelemetry exists to close that gap — and in the .NET ecosystem, it's matured from an experimental curiosity into the de facto standard for instrumentation. This post covers everything you need to go from zero to production-grade observability in your .NET microservices, with concrete C# examples, real debugging scenarios, and deployment patterns for Azure.…