Understanding Observability: Metrics, Traces, and Logs

Modern systems are distributed, dynamic, and constantly changing. Microservices, cloud platforms, containers, and serverless architectures make traditional monitoring insufficient on its own.

Observability is the ability to understand what is happening inside a system by analyzing the data it produces — without deploying new code or guessing.

This article explains the three pillars of observability — metrics, logs, and traces — and how they work together to help engineers diagnose issues, improve reliability, and operate systems at scale.

Observability vs Monitoring

Monitoring answers known questions: “Is the CPU high?” or “Is the service up?”

Observability answers unknown questions:

Why is this request slow for only some users, in one region, under specific conditions?

Observability focuses on exploration, not just predefined alerts.

Metrics: Measuring System Health

Metrics are numeric measurements collected over time. They provide a high-level view of system performance and capacity.

Common Metric Types

• CPU, memory, and disk utilization
• Request rate and throughput
• Error rates
• Latency percentiles (p50, p95, p99)

Metrics are efficient to store and query, making them ideal for dashboards and alerting.

Logs: Context and Detail

Logs are discrete, timestamped records of events. They provide detailed context about what happened inside an application or system.

Effective Logging Practices

• Use structured logging (JSON)
• Include request IDs and user context
• Log errors with actionable detail
• Avoid excessive or sensitive data

Logs are invaluable for root-cause analysis, but difficult to use alone at scale.

Traces: Following a Request End-to-End

Traces track a single request as it flows through multiple services and components.

Each trace is composed of spans, which represent individual operations.

Traces reveal where latency and failures actually occur.

Tracing is essential for understanding performance in microservice and distributed architectures.

How Metrics, Logs, and Traces Work Together

True observability emerges when these signals are correlated using shared identifiers.

Common Observability Mistakes

• Relying only on metrics
• Unstructured or noisy logs
• No trace propagation between services
• Alerting on symptoms, not causes
• Ignoring observability costs

Observability in Cloud-Native Systems

Cloud platforms generate massive amounts of telemetry. Observability tools must scale horizontally and integrate with orchestration systems.

• Prometheus and OpenTelemetry
• Centralized log aggregation
• Distributed tracing backends

Final Thoughts

Observability is not a tool — it is a design principle.

Systems built with observability in mind are easier to debug, more reliable, and safer to operate at scale.