What is Observability
Observability — the ability to understand a system's internal state from its external outputs. Three pillars: **metrics** (numbers over time — CPU, QPS), **logs** (events — errors, audit trail), **traces** (request path across distributed services). Difference from monitoring: monitoring = knowing known unknowns (CPU high). Observability = exploring unknown unknowns (new bug type).
Below: details, example, related terms, FAQ.
Details
- Metrics: Prometheus, Grafana, Datadog, New Relic. Aggregated, efficient
- Logs: Loki, ELK stack, CloudWatch. Full-text, expensive at scale
- Traces: Jaeger, Zipkin, Tempo. Per-request detailed flow
- Correlation: trace_id links all 3 (standardised via OpenTelemetry)
- Cardinality explosion: high-cardinality labels (user_id) kill Prometheus
Example
// OpenTelemetry instrumented code
const tracer = trace.getTracer('my-app');
const span = tracer.startSpan('db-query');
try {
await db.query('SELECT ...')
} finally {
span.end(); // exports trace to Jaeger/Tempo
}Related Terms
Learn more
Frequently Asked Questions
Observability vs Monitoring?
Monitoring = alerts on predetermined conditions. Observability = ad-hoc investigation via exploration. Overlap is big but observability goes deeper.
Do I need all 3 pillars?
Minimum: metrics + logs. Traces — when you have microservices/distributed. In a monolith start with the first two.
Stack suggestions?
Small team: Datadog (SaaS, all-in-one) or Grafana Cloud (cheaper). Self-host: Prometheus + Loki + Tempo + Grafana (LGTM).