Distributed Tracing

Distributed tracing is a way to follow a single request as it travels across all the services, queues, and databases that handle it in a distributed or microservices system. Each step attaches a shared trace ID and records a timed "span," and a tracing tool stitches these spans into one end-to-end timeline showing exactly where the request went and how long each hop took. In a monolith a stack trace tells you what happened; once you split into many services, no single log does, and distributed tracing is what reconstructs the full journey. It's one of the three pillars of observability alongside logs and metrics, and OpenTelemetry is the emerging vendor-neutral standard for producing traces. For AI/SaaS builders it's how you answer "why is this API call slow?" when the answer is buried three services deep — the trace shows the one span that took 800ms. Practical note: instrument with OpenTelemetry early and propagate the trace context across every service boundary, because a trace with a broken chain only tells half the story.