ECS

When we measured a full ECS blue/green deployment in the first post of this series, one number stood out: 28 seconds. That’s how long the new revision sits on the test listener before production traffic shifts to it, and it’s the only period in which a smoke test could stop a bad release before users see it. No realistic test suite fits in that time. Pause hooks are the fix. Announced in May 2026, they make the deployment stop at a stage you choose and wait for you, turning those 28 seconds into a smoke test phase of whatever length you need. Third-party coverage of the feature is still close to zero, so we measured the whole workflow on our test stack: the continue path, the rollback path, an alarm firing mid-pause, and one case where the hook is accepted and then does nothing at all. Every number below comes from a measured run (July 2026, eu-west-1).

In July 2025, ECS introduced a native blue/green deployment type comprising two target groups, a test listener, a bake period and managed rollback, all of which are run by ECS itself with no involvement from CodeDeploy. The documentation covers the ideal scenario. However, it says much less about how the feature behaves with CloudFormation on top, such as where UPDATE_COMPLETE lands relative to the bake, how long each stage really takes and whether stack updates end up conflicting with the listener rules that the feature rewrites. We built a small test stack and ran the machinery repeatedly, documenting everything. This post opens a series on how ECS deployment strategies behave when driven by CloudFormation - every number in it comes from a measured run.