Progressive Delivery

Progressive delivery takes strategies covered in deployment-strategies — canary, blue-green — and makes the promotion decision automatic and metric-driven instead of manual or time-based. A canary that "runs for ten minutes then goes to 100%" is not progressive delivery, it's a timer with extra steps: if the ten minutes happened not to expose the regression, you ship it anyway. The controller (Argo Rollouts, Flagger) exists to query real signals at each step and decide, without a human in the loop, whether to advance, hold, or abort.

A canary step that isn't gated on a query against production metrics is just a delay, not a safety mechanism.

1. Pick metrics that would actually catch a bad release