# ECS Blue/Green Checklist (July 2026)

Two supported paths — pick one deliberately:

| Path | Controller | Best when |
| --- | --- | --- |
| **ECS native B/G** | `deploymentController.type=ECS` + `strategy=BLUE_GREEN` | Want traffic shift inside ECS (ALB/NLB/Service Connect); fewer CodeDeploy moving parts |
| **CodeDeploy B/G** | `deploymentController.type=CODE_DEPLOY` | Need CodeDeploy linear/canary presets, appspec hooks, existing CD pipelines |

## Shared prerequisites

- [ ] Two target groups (blue/green) + listener rule weights
- [ ] Container `/health` that reflects readiness (not just process up)
- [ ] CloudWatch alarms wired to auto-rollback
- [ ] Pre/post traffic validation (Lambda hook or ECS lifecycle hook)

## CodeDeploy configs (if using CODE_DEPLOY)

Prefer `CodeDeployDefault.ECSCanary10Percent5Minutes` or linear presets over all-at-once for risky releases.

## Dual-run cost

Blue + green capacity during the window — budget minutes × 2× task count; keep blue until alarms stay green.