A few months ago I was freelancing on a client project. Every API call was slow. Some were taking 800ms, some 1.2 seconds — but nobody could pinpoint why. The codebase touched 6 services. Debugging meant manually correlating logs across all of them, file by file, hoping to find where time was being lost. It took hours per incident. That experience made me ask a question I couldn't let go of: Is there a way to get a blueprint of every function, service, and database call that happens for a single API request — automatically? That led me to Jaeger, Zipkin, and the OpenTelemetry protocol. I was genuinely impressed that someone had built a system that could trace the entire path of an API call and tell you exactly where latency occurs. Then I did what any curious engineer would do — I decided to build my own. What I Built Lumen — a self-hosted distributed tracing system that collects, stores, and analyzes traces from your microservices using OpenTelemetry.…