Observability

Where it shows up in real systems

• Metrics

  The four golden signals tell you something is wrong before users do. Without metrics, failures are only noticed when customers complain, which multiplies recovery time.

  In production: Prometheus, Datadog, Amazon CloudWatch, Grafana Mimir

• Centralised logs

  Indispensable to understand an incident after the fact. Volume grows fast, so set retention and log levels deliberately.

  In production: Elasticsearch + Kibana, Grafana Loki, Datadog Logs, Splunk

• Distributed tracing

  Shows which hop is slow in a chain of microservices. Sampling keeps the cost down while still catching tail latency.

  In production: OpenTelemetry, Jaeger, Grafana Tempo, AWS X-Ray, Honeycomb

• Service mesh

  Moves resilience and security out of application code into infrastructure, with uniform telemetry for every call. Each hop pays a little latency and the mesh itself is critical infrastructure to operate.

  In production: Istio, Linkerd, Consul Connect, AWS App Mesh, Cilium