# Canary Releases — CI/CD Fundamentals: Pipelines, Testing and Deployment

Source: https://www.skillbyai.com/en/cicd/cicd-deploy-canary

> Release to a small slice of traffic first with canary deployments and widen only when metrics look healthy.

## How it works

Route a small percentage of real traffic (say 5%) to the new version while the rest keeps hitting the old one. If metrics stay healthy, gradually increase the percentage until it's 100%.

## Canary in a coal mine

Miners once carried a canary into the tunnel — if it stopped singing, they knew danger was present before it reached them. A canary release exposes the new version to a small group first, as an early-warning signal.

## Watch the right metrics

Error rate, latency, and business metrics (checkout success) on the canary slice — not just 'is it up'. Widen only when those numbers match or beat the baseline.