What 'Observability' Means for Web Infrastructure

Observability, in the engineering sense, is the ability to understand the internal state of a system by examining its external outputs. For web infrastructure, that means being able to answer 'why is this slow' or 'where is this traffic coming from' without guessing.

The three pillars

• Metrics: numeric measurements over time. Request rate, latency percentiles, error rate, CPU usage. Good for detecting that something is wrong.
• Logs: structured event records. Each request, each error, each decision. Good for understanding what happened in a specific request.
• Traces: end-to-end records of how a request moved through distributed services. Good for pinpointing where latency was introduced.

Why they're not enough alone

Metrics tell you something is wrong but not why. Logs tell you what happened to individual requests but are hard to query at scale. Traces show the path but require instrumentation across every service. Observability requires all three, correlated.

The security dimension

For security, observability means being able to answer: why was this request blocked, where did this attack originate, and is my security posture improving or degrading. That requires the same three pillars applied to the security layer, not just the application layer.