| Pillar | What it is | Example tools |
|---|---|---|
| Metrics | Numeric time-series data (CPU %, request rate, error count) | Prometheus, CloudWatch, Datadog metrics, Azure Monitor |
| Logs | Discrete event records (text or structured JSON) | Loki, ELK / Elastic, CloudWatch Logs, Splunk, Datadog logs |
| Traces | Records of a request's journey across services | Jaeger, Tempo, AWS X-Ray, Datadog APM |
Modern observability stacks combine all three with consistent context (request ID, trace ID) so you can pivot between them.