Great question — you can absolutely run Prefect with an AWS/ECS-based backend. Here’s a concise, end-to-end path for Prefect 3.x that works well when your code runs in containers and you want Prefect to orchestrate your workflows on ECS. High-level architecture - You create an ECS Work Pool in Prefect Cloud. - You run a Prefect ECS worker (typically as a long-running ECS service), which polls your Work Pool. - You deploy flows that target that Work Pool; the worker launches each flow run as an ECS task using your task definition/image/network settings. Step-by-step 1) Install and authenticate - Install Prefect and the AWS integration on the machine/container that will run your Prefect worker:

pip install -U prefect prefect-aws

- Log in to Prefect Cloud:

prefect cloud login --key <YOUR_API_KEY> --workspace <account>/<workspace>

Docs: - ECS guide - prefect.yaml deployments 2) Create an ECS Work Pool - Create a pool of type ecs:

prefect work-pool create my-ecs-pool --type ecs

- Get the default ECS base job template to customize:

prefect work-pool get-default-base-job-template --type ecs > ecs-template.json

This template includes all the fields the worker needs (image, cluster, cpu/memory, task/execution roles, network config, CloudWatch logs, etc.). 3) Customize the base job template for your environment - Edit ecs-template.json to specify: - image: ECR image for your flow container - cluster: your ECS cluster name/ARN - launch_type: typically "FARGATE" (or configure capacity providers) - container_name: container in your task definition (e.g., "flow") - cpu/memory: task sizes, e.g., "512"/"1024" - execution_role_arn and task_role_arn - network_configuration (VPC/Subnets/SecurityGroups) - optionally task_definition_arn if you want to use a pre-registered definition instead of letting Prefect register one Example snippet (minimal):

{
  "job_configuration": {
    "task_definition": {
      "containerDefinitions": [
        {
          "image": "<http://123456789012.dkr.ecr.us-east-1.amazonaws.com/prefect-flows:latest|123456789012.dkr.ecr.us-east-1.amazonaws.com/prefect-flows:latest>",
          "name": "flow"
        }
      ],
      "cpu": "512",
      "memory": "1024",
      "executionRoleArn": "arn:aws:iam::123456789012:role/ecsTaskExecutionRole",
      "family": "prefect-flows"
    },
    "task_run_request": {
      "launchType": "FARGATE",
      "cluster": "my-ecs-cluster",
      "overrides": {
        "containerOverrides": [
          {
            "name": "flow"
          }
        ],
        "taskRoleArn": "arn:aws:iam::123456789012:role/prefect-task-role"
      },
      "networkConfiguration": {
        "awsvpcConfiguration": {
          "subnets": [
            "subnet-abc",
            "subnet-def"
          ],
          "securityGroups": [
            "sg-123456"
          ],
          "assignPublicIp": "ENABLED"
        }
      }
    },
    "configure_cloudwatch_logs": true,
    "cloudwatch_logs_prefix": "/prefect/flows",
    "container_name": "flow"
  }
}

- Save and apply it to the work pool:

prefect work-pool update my-ecs-pool --base-job-template ecs-template.json

IAM and permissions (important) - The worker’s AWS credentials must be able to: - ecs:RunTask, ecs:DescribeTasks, ecs:StopTask - ecs:RegisterTaskDefinition, ecs:DeregisterTaskDefinition (if you let Prefect register task defs) - iam:PassRole for the task role and execution role used by your tasks - Your task execution role should have the AmazonECSTaskExecutionRolePolicy (pulls from ECR, writes CloudWatch logs). - If pulling from ECR private repos, ensure the execution role/ECS is allowed to pull images. 4) Run a Prefect ECS worker - Run the worker anywhere that has AWS access (commonly as its own ECS service with a task role), then:

prefect worker start --pool my-ecs-pool

Tip: Ensure the worker container has AWS credentials (via task role, or environment variables like AWS_REGION, AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY). 5) Create your first deployment Option A: Use a Docker image that contains your flows - Ensure your flow code is in the ECR image you referenced in ecs-template.json. - Initialize a Prefect project and add a deployment:

prefect init

- Edit prefect.yaml to define a deployment targeting your ECS pool and (optionally) override any job_variables from the base job template:

name: my-project
prefect-version: ">=3.0.0"

deployments:
- name: etl
  entrypoint: flows/etl.py:etl
  work_pool:
    name: my-ecs-pool
    job_variables:
      image: <http://123456789012.dkr.ecr.us-east-1.amazonaws.com/prefect-flows:latest|123456789012.dkr.ecr.us-east-1.amazonaws.com/prefect-flows:latest>
      cluster: my-ecs-cluster
      launch_type: FARGATE
      container_name: flow
      cpu: "512"
      memory: "1024"
      task_role_arn: arn:aws:iam::123456789012:role/prefect-task-role
      execution_role_arn: arn:aws:iam::123456789012:role/ecsTaskExecutionRole
      network_configuration:
        awsvpcConfiguration:
          subnets: ["subnet-abc", "subnet-def"]
          securityGroups: ["sg-123456"]
          assignPublicIp: ENABLED

- Deploy:

prefect deploy

Option B: Source-based deployments (clone your repo at run time) - You can do:

from prefect import flow
flow.from_source(
    "<https://github.com/your-org/your-repo>",
    entrypoint="flows/etl.py:etl",
).deploy(name="etl", work_pool_name="my-ecs-pool")

- In this case, your base image must include your Python dependencies; the worker will pull code at runtime. 6) Kick off a flow run - From the CLI:

prefect deployment ls
prefect deployment run "etl/etl"

- From your backend (if you want to trigger from your app running on ECS), add Prefect as a dependency and call:

from prefect.deployments import run_deployment
run = run_deployment(name="etl/etl", parameters={"param": "value"})

Make sure your backend container has PREFECT_API_URL and PREFECT_API_KEY set to reach Prefect Cloud. Common gotchas - Make sure the container_name in your template matches the container in your task definition. - If you see permission errors, add iam:PassRole for both task and execution roles to the worker’s principal. - For Fargate, use awsvpc networking with subnets/SGs and assignPublicIp if needed for outbound internet. - In Prefect 3.x, use

prefect deploy

and work pools; do not use deprecated 2.x commands like

prefect deployment build

or

Deployment.build_from_flow()

. Helpful docs - ECS guide: Run flows on AWS ECS - Prefect YAML: prefect.yaml reference A few questions to tailor this for you - Are you using Fargate or EC2-backed ECS? - Do you already have an ECR image for your flow code, or do you prefer cloning from a Git repo at runtime? - Do you want the Prefect worker to run as its own ECS service in your cluster? - Which VPC, subnets, and security groups should tasks run in? - Do you want logs in CloudWatch in addition to Prefect Cloud logs? If you share those, I can provide a ready-to-use ecs-template.json and prefect.yaml for your setup.

Yes — you can use Prefect for free by self-hosting Prefect Server (open-source) on your own cloud infra, then run your flows on ECS using your ECR image. Since you’re on EC2 and have an ECR image, here’s a clean path to get this running with Prefect 3.x. High-level - Run Prefect Server (OSS) on your own EC2 (or as containers you manage). - Point your code/worker to your Server via PREFECT_API_URL. - Create an ECS work pool (type ecs) and start a Prefect ECS worker. - Deploy flows targeting that work pool; each run will launch an ECS task using your ECR image. 1) Stand up Prefect Server (self-hosted, free) - Install Prefect on an EC2 instance and start the server:

pip install -U prefect
prefect server start --host 0.0.0.0 --ui

- Expose it via your load balancer/reverse proxy with TLS in front. Set on every client (your dev machine, worker containers, etc.):

prefect config set PREFECT_API_URL=http(s)://<your-server-host>:<port>/api

- For production, run Server as a service (and consider Postgres, backups, and restricted network access). CLI help we verified: -

prefect server start --help

2) Install AWS integration on the machine that will run your worker

pip install -U prefect prefect-aws

3) Create an ECS Work Pool - Create:

prefect work-pool create my-ecs-pool --type ecs

- Get and customize the ECS base job template:

prefect work-pool get-default-base-job-template --type ecs > ecs-template.json

Edit ecs-template.json with your details. Since you’re using EC2-backed ECS capacity, set launch_type to EC2 and reference your ECR image and roles: Example ecs-template.json (minimal EC2 example)

{
  "job_configuration": {
    "task_definition": {
      "family": "prefect-flows",
      "cpu": "512",
      "memory": "1024",
      "executionRoleArn": "arn:aws:iam::123456789012:role/ecsTaskExecutionRole",
      "containerDefinitions": [
        {
          "name": "flow",
          "image": "<http://123456789012.dkr.ecr.us-east-1.amazonaws.com/prefect-flows:latest|123456789012.dkr.ecr.us-east-1.amazonaws.com/prefect-flows:latest>",
          "essential": true
        }
      ]
    },
    "task_run_request": {
      "launchType": "EC2",
      "cluster": "my-ecs-cluster",
      "overrides": {
        "taskRoleArn": "arn:aws:iam::123456789012:role/prefect-task-role",
        "containerOverrides": [
          {
            "name": "flow"
          }
        ]
      }
      /* For EC2 launch type, only include networkConfiguration if you're using awsvpc on your container instances.
         If your tasks use bridge/host networking, omit networkConfiguration here. */
    },
    "container_name": "flow",
    "configure_cloudwatch_logs": true,
    "cloudwatch_logs_prefix": "/prefect/flows"
  }
}

Apply it:

prefect work-pool update my-ecs-pool --base-job-template ecs-template.json

IAM requirements (common) - The worker’s AWS principal needs: ecs:RunTask, ecs:DescribeTasks, ecs:StopTask; iam:PassRole for your task/execution roles; and if Prefect should register task definitions: ecs:RegisterTaskDefinition and ecs:DeregisterTaskDefinition. - The execution role should have AmazonECSTaskExecutionRolePolicy (ECR pulls, CloudWatch logs). 4) Start a Prefect ECS worker Run this as a long-lived process (systemd on EC2 or an ECS service) with AWS access and PREFECT_API_URL pointing at your Server:

prefect worker start --pool my-ecs-pool

5) Package your flow and create a deployment Since you already have an ECR image with your code, point deployments at that image and the ECS pool. - Initialize a Prefect project (in your repo):

prefect init

- Edit prefect.yaml to target your pool and (optionally) override per-deployment job variables: ``` name: my-project prefect-version: ">=3.0.0" deployments: - name: etl entrypoint: flows/etl.py:etl work_pool: name: my-ecs-pool job_variables: image: 123456789012.dkr.ecr.us-east-1.amazonaws.com/prefect-flows:latest cluster: my-ecs-cluster launch_type: EC2 container_name: flow

cpu: "512" memory: "1024" task_role_arn: arnawsiam:123456789012role/prefect-task-role execution_role_arn: arnawsiam:123456789012role/ecsTaskExecutionRole

- Create the deployment:

prefect deploy

6) Run your flows
- Trigger from CLI:

prefect deployment run "etl/etl"

- Or from code (pointing to your Server via PREFECT_API_URL):

from prefect.deployments import run_deployment run_deployment(name="etl/etl", parameters={"foo": "bar"})

Optional but recommended
- Persist results/logs to AWS services:
  - Results to S3 (configure in your flow/deployment or via settings).
  - Logs to CloudWatch (set in ecs-template.json as shown).
- Network posture:
  - For ECS EC2 with awsvpc networking, ensure your container instances and tasks are in the proper subnets/SGs (and NAT/IGW for outbound if needed).

Docs and references
- ECS guide: <https://docs-3.prefect.io/integrations/prefect-aws/ecs_guide|Run flows on AWS ECS>
- prefect.yaml reference: <https://docs-3.prefect.io/v3/how-to-guides/deployments/prefect-yaml|prefect.yaml deployments>
- CLI we used: ```prefect server start

,

prefect work-pool create --type ecs

,

prefect work-pool get-default-base-job-template --type ecs

,

prefect work-pool update --base-job-template

,

prefect worker start

,

prefect deploy

A couple of quick questions to tailor this precisely: - Do you want to run the Prefect worker as an ECS service or as a systemd service on an EC2 instance? - Are your ECS tasks using awsvpc networking on EC2 container instances, or bridge/host? - Do you prefer Prefect to register task definitions automatically, or will you provide a fixed taskDefinition ARN? If you share those, I can provide a ready-to-paste ecs-template.json and prefect.yaml matching your exact setup.