Datadog
APM & Distributed Tracing
Trace a request across services to find where latency and errors come from.
Datadog APM instruments your application to emit traces — a trace is the full journey of one request, made of spans where each span is one unit of work (an HTTP handler, a DB query, a cache call). Spans carry timing, the service and resource name, tags, and parent/child links, so a flame graph reconstructs exactly where time went.
A parcel tracking history that timestamps every depot the package passed through. When delivery is late, the timeline shows exactly which depot held it up rather than just "it was slow".
Key Concepts
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Instrumentation is usually automatic: a per-language tracing library hooks common frameworks and clients with little or no code change. Datadog ties traces to the service catalog and to metrics generated from spans (request rate, error rate, latency percentiles — the "RED" signals), so you can move from a p99 latency alert straight into the slow traces behind it, then to the logs of that exact request via a shared trace ID.