Glossary

Anomaly detection

Anomaly detection identifies measurements that deviate significantly from a metric learned normal behaviour, rather than comparing against a fixed threshold.

Short answer

What is anomaly detection?

Anomaly detection identifies measurements that deviate significantly from a metric learned normal behaviour, rather than comparing against a fixed threshold.

Explained two ways

Plain and technical

In plain terms

Instead of alerting when a number crosses a line somebody guessed, anomaly detection learns what normal looks like for that specific measurement (including that Monday mornings are busy), and alerts when it departs from that.

Technically

Effective anomaly detection models seasonality at hourly and weekly granularity, detects deviation in both directions since an unexpected drop is often more significant than a rise, and groups co-moving detections into single findings. Feedback should update the baseline rather than adding suppression rules, which otherwise accumulate until nothing is reported.

Example

What it looks like in practice

Request rate falls to a third of its normal Tuesday morning level. No error threshold was crossed and nothing appeared broken, but the deviation is detected and investigated: an upstream routing change was silently dropping traffic.
Keep going

More definitions

See these concepts in a running system

A 30-minute walkthrough against your own infrastructure rather than a slide about the theory.