Observability: Why Metrics Alone Are Not Enough

Metrics answer only part of the question

Metrics are essential for monitoring infrastructure. CPU utilization, memory usage, request rate, latency, and error rate can quickly show that something has changed. But metrics usually tell you what happened. They do not always tell you why.

Imagine a latency spike

Suppose application latency suddenly increases. A dashboard may clearly show the problem. Request latency has doubled. Error rates are increasing. CPU utilization looks normal. At this point, metrics have identified the symptom. But engineers still need to find the cause.

Logs add context

Logs provide detailed events generated by applications and infrastructure. They may reveal:

• database timeout errors
• authentication failures
• application exceptions
• failed external API requests
• configuration problems

Logs help explain what individual components were doing when the incident occurred. But in a distributed architecture, searching through logs from many different services can still be difficult.

Traces connect the request path

Distributed tracing follows a request as it moves through multiple services. A single user request might pass through: API Gateway → authentication service → application service → database → external API. A trace shows how much time was spent in each stage. This makes it much easier to identify where latency or failure originated.

Metrics, logs, and traces work together

Each signal provides a different perspective. Metrics answer: “What changed?” Logs answer: “What happened inside the component?” Traces answer: “Where did this request spend its time?” Together, they provide a much more complete picture of system behavior.