Great question — you don’t need to keep redeploying just to change the ECS task definition ARN. A few ways to simplify this in Prefect 3.x: 1) Move the ARN out of the deployment and into the work pool - Put

task_definition_arn

in the ECS work pool’s Base Job Template instead of the deployment’s job variables. - Then when the task definition changes, just update the work pool — no code changes or CI/CD redeploys needed. - UI path: Work Pools -> your ECS pool -> Edit Base Job Template -> update “Task definition ARN”. - Docs: Customize job variables 2) Don’t pin an ARN — let the worker register the task definition - If you omit

task_definition_arn

, the ECS worker will use the work pool’s job variables (image, cpu, memory, roles, env, network) to register a task definition on demand. - This makes Prefect the source of truth for the TD config so you don’t need to sync with an external AWS-managed TD. - Docs: ECS guide 3) Use a dynamic value via Jinja and update it externally - Set

task_definition_arn

in the Base Job Template to read from an environment variable or Prefect Variable: - Example in your Base Job Template:

{
  "task_definition_arn": "{{ env.get('ECS_TASK_DEFINITION_ARN') }}"
}

or

{
  "task_definition_arn": "{{ variables.get('ECS_TASK_DEFINITION_ARN') }}"
}

- When a new TD is published in AWS, update the env var on the worker or the Prefect Variable (you can automate this with a short script using boto3). No redeploy required. - Docs: Customize job variables Notes on “latest” by family - ECS RunTask supports passing a family name to use the latest ACTIVE revision. Prefect’s field is named

task_definition_arn

, and we haven’t found official docs guaranteeing that a family name (e.g.,

my-family

) will be passed through unchanged. If you want to try this, I can help you test it — but the supported approaches above are safer. If you tell me which direction you prefer (work pool as the single place to update, Prefect-managed TDs, or a dynamic value), I can share exact steps/snippets tailored to your current setup.