Great questions. Here’s a concise checklist you can give your cloud engineer plus answers to your specific questions. Assumptions - Prefect 3.x - You’ll run Prefect Server and the worker on your single EC2 instance in ap-southeast-1. - Flow runs will execute on AWS ECS Fargate. - No Redis. What to ask your cloud engineer to create/provide 1) ECS and networking - ECS cluster: - Region: ap-southeast-1 - Capacity providers: FARGATE (optionally FARGATE_SPOT) - Cluster name (return this to you) - VPC details for Fargate tasks: - VPC ID - Private subnet IDs (recommended) or public if you prefer - Security group for tasks: - Outbound to: - Prefect Server API (see “Prefect Server connectivity” below) - ECR, CloudWatch Logs, STS (via NAT or VPC endpoints) - CloudWatch Logs: - Log group name (e.g., /prefect/flows) - Retention policy - ECR: - ECR repo URI(s) for your flow image(s) if using private images (optional if you’ll use public Prefect images) 2) IAM roles and policies - ECS task execution role (for the flow-run tasks): - Attach AWS managed: AmazonECSTaskExecutionRolePolicy - Add ECR read permissions if pulling from private ECR - Add CloudWatch Logs permissions if needed - If you’ll read secrets from AWS Secrets Manager/SSM in the task container, add read access - Return the role ARN - ECS task role (runtime permissions for your flow code): - Least-privilege policies to access the AWS services your flows need (e.g., S3, Secrets Manager, RDS auth, etc.) - Return the role ARN - Worker’s IAM principal (how the worker calls ECS): - Since you’ll run the worker on your EC2 host, attach an instance profile role with these permissions: - ecs:RunTask, ecs:StopTask, ecs:DescribeTasks, ecs:DescribeTaskDefinition, ecs:RegisterTaskDefinition, ecs:DeregisterTaskDefinition, ecs:DescribeClusters - iam:PassRole limited to the ARNs of your ECS task execution role and ECS task role - Optional (only if you want the worker to auto-create log groups): logs:CreateLogGroup - Example policy for the worker principal (tighten ARNs to your environment):

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "ECSControl",
      "Effect": "Allow",
      "Action": [
        "ecs:RunTask",
        "ecs:StopTask",
        "ecs:DescribeTasks",
        "ecs:DescribeTaskDefinition",
        "ecs:RegisterTaskDefinition",
        "ecs:DeregisterTaskDefinition",
        "ecs:DescribeClusters"
      ],
      "Resource": "*"
    },
    {
      "Sid": "PassRolesToTasks",
      "Effect": "Allow",
      "Action": "iam:PassRole",
      "Resource": [
        "arn:aws:iam::<account-id>:role/<ecs-task-execution-role-name>",
        "arn:aws:iam::<account-id>:role/<ecs-task-role-name>"
      ]
    },
    {
      "Sid": "OptionalCreateLogsGroup",
      "Effect": "Allow",
      "Action": [
        "logs:CreateLogGroup"
      ],
      "Resource": "*"
    }
  ]
}

3) Prefect Server connectivity from Fargate tasks - Ensure every Fargate task can reach PREFECT_API_URL: - If your Prefect Server API is private on the EC2 host, put it behind an internal ALB/NLB and provide a private URL (recommended). Open the target SG/port to the ECS tasks’ SG. - If public, provide a public URL and open the EC2 SG/port appropriately. - Share with you the final URL you should set as PREFECT_API_URL (e.g., http(s)//internal alb.your.domain4200 or 443 if behind TLS). 4) Optional VPC endpoints (to avoid NAT costs and public egress) - Consider interface/gateway endpoints for: ECR (api+dkr), CloudWatch Logs, Secrets Manager/SSM, STS. Otherwise ensure a NAT gateway for internet egress. How many ECS services do you need? - For Prefect flow runs on ECS Fargate: zero services. Prefect uses ecs:RunTask to launch tasks on demand.

- You only need an ECS Service if you choose to run the long‑lived Prefect worker itself on ECS. Since you plan to run the worker on your EC2 host, you don’t need any ECS service. Do you need access keys for the ECS task execution role? - No. Do not use the task execution role’s keys. - The task execution role is assumed by ECS on behalf of your task to pull images and write logs. - Your worker needs its own AWS credentials to call the ECS API (best: use the EC2 instance profile role with the policy above). Access keys are not required if you use an instance profile. What you’ll configure in Prefect (high level) - Create an ECS work pool in Prefect and set: - cluster: <your-ecs-cluster-name> - subnets: [<subnet-ids>] - security groups: [<sg-ids>] - task execution role ARN and task role ARN - log group name - image (public Prefect image or your ECR image) - Start a worker process on your EC2 host that points to this work pool. Ensure that worker process has AWS permissions listed above and can reach your Prefect Server API. Helpful docs - Prefect ECS guide: Prefect AWS ECS guide - Workers and work pools overview: Workers and Work Pools - AWS: Task execution role vs task role: ECS task execution role docs Open questions for you - Do you want the Prefect worker to run on your EC2 host (recommended for your setup) or as an ECS service? - Will your flow images live in private ECR, or will you use the public Prefect images? - Is your Prefect Server API going to be private (internal LB) or public? I can help finalize the exact PREFECT_API_URL and SG rules once you confirm.

Got it — you want to run the Prefect worker itself on ECS (Fargate) and have it launch flow runs as ECS tasks. Here’s what to give your cloud engineer and how many services you’ll need. What your cloud engineer should provision ECS cluster and networking - ECS cluster: - Region: ap-southeast-1 - Capacity providers: FARGATE (optionally FARGATE_SPOT) - Cluster name - VPC/subnets/security groups for Fargate: - Private subnets (recommended) - Security group for tasks that allows: - Outbound to Prefect Server API URL (see below) - Outbound to ECR, CloudWatch Logs, STS (via NAT or VPC endpoints) - CloudWatch Logs: - Log group for the worker (e.g., /prefect/worker) and one for flow runs (e.g., /prefect/flows) - Retention policy - ECR: - Repo for your flow images (if private) - Worker image can be public (e.g., prefecthq/prefect:3-latest) or pinned; you can also host your own worker image in ECR IAM roles and policies (separate worker from flow-run permissions) - For the worker service task (long‑lived): - Worker task execution role (standard ECS execution): - Attach AWS managed: AmazonECSTaskExecutionRolePolicy - ECR read permissions if pulling from private ECR - CloudWatch Logs write permissions - Worker task role (runtime perms for the worker to control ECS): - ecs:RunTask, ecs:StopTask, ecs:DescribeTasks, ecs:DescribeTaskDefinition, ecs:RegisterTaskDefinition, ecs:DeregisterTaskDefinition, ecs:DescribeClusters - iam:PassRole limited to the ARNs of the flow-run task execution role and flow-run task role - Optional: logs:CreateLogGroup if you want the worker to auto-create log groups - For flow-run tasks (on‑demand): - Flow task execution role: - AmazonECSTaskExecutionRolePolicy - ECR read (if private), CloudWatch Logs write - Flow task role: - Least-privilege access to AWS services your flows need (e.g., S3/Secrets Manager/RDS/etc.) Prefect Server connectivity (critical) - Every worker and flow task must reach PREFECT_API_URL. - Since your Server runs on EC2, expose it via: - Internal ALB/NLB (recommended) with a private URL, or - Public URL, if you’re okay with internet exposure - Open security groups so ECS tasks can reach the Server on the API port. - PREFECT_API_URL format for Prefect 3.x Server is:

http://<host-or-lb>:4200/api

or https if terminated at your LB. Optional to reduce NAT costs - Add VPC endpoints for: ECR (api + dkr), CloudWatch Logs, STS, Secrets Manager/SSM. How many ECS services do you need? - One ECS Service to run the Prefect ECS worker (desiredCount=1 is fine to start). - You do NOT create services for flow runs — the worker uses ecs:RunTask to launch them on demand. - For multiple environments: - Best practice: one work pool + one ECS Service (worker) per environment (dev/stage/prod) for clear isolation and blast-radius control. - You can scale desiredCount>1 for HA, or run multiple worker services if you want separate queues or capacity. Do you need access keys for the ECS task execution role? - No. Do not create or use access keys for execution roles. - The ECS service assumes the worker’s execution and task roles automatically. - Whoever deploys the ECS service (your CI/CD or engineer) needs permissions like ecs:CreateService/UpdateService and iam:PassRole to pass the worker roles — but not the worker/flow execution role’s access keys. What to put in the worker service/task definition - Container image: prefecthq/prefect:3-latest (or your bespoke image) - Command:

prefect worker start --pool <your-ecs-pool-name>

- Environment variables: - PREFECT_API_URL: http(s)//&lt;your server&gt;4200/api - Any other Prefect settings you need (e.g., PREFECT_LOGGING_LEVEL) - CPU/memory: start small (e.g., 0.25 vCPU/512–1024MB) and adjust - Networking: awsvpc in your private subnets, SG as above - IAM roles: attach the worker task execution role and worker task role

Prefect setup steps (once infra is ready) - Create an ECS work pool:

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

- Inspect default ECS job template to see what variables you’ll configure (cluster, subnets/SGs, image, roles, logs):

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

- Configure the pool’s base job variables for: - cluster, launch_type=FARGATE (or capacityProviderStrategy) - network_configuration (subnets, security groups, assignPublicIp=false if using private subnets) - image (your flow image), execution_role_arn, task_role_arn - cloudwatch_logs options (log group name) - Deploy the worker ECS Service using the task definition above. Docs - Prefect AWS ECS guide: Prefect AWS ECS guide - Workers and Work Pools overview: Workers and Work Pools - AWS: ECS task execution role: ECS task execution role Quick confirmations to tailor this: - Will you split dev/stage/prod into separate work pools and worker services? - Are your flow images in private ECR? - Is your Prefect Server API going to be internal (ALB/NLB) or public? I can help finalize the exact pool variables and security groups once you confirm.

Short answer - You do NOT need an inbound rule on the ECS service/tasks for Prefect. The worker and your flow-run tasks are clients; they only make outbound calls to your Prefect Server API and AWS services. - You DO need your Prefect Server’s security group to allow inbound from the ECS tasks to port 4200 (ideally from the ECS tasks’ security group or VPC CIDR, not 0.0.0.0/0). - ECS control plane/cluster is free. You pay for: - The worker ECS Service task (runs 24/7 if you host the worker on Fargate). - Each flow-run Fargate task while it’s running. - Plus any supporting infra (NAT gateway or VPC endpoints, CloudWatch Logs, ECR storage/transfer). Details Security groups and connectivity - Prefect Server on EC2: - Keep inbound 4200 open only to the source you need: - If using an internal ALB/NLB: allow inbound from the ALB’s SG on 4200. - If direct access: allow inbound from the ECS tasks’ SG or your VPC CIDR. - ECS worker/flow tasks: - No inbound rules needed. - Outbound must allow: - HTTPS to ECR, CloudWatch Logs, STS, etc. (via NAT or VPC endpoints) - HTTP/HTTPS to your Prefect Server API URL (format: http(s)//&lt;host or lb&gt;4200/api) - If the tasks and Server are in the same VPC/subnets, they can talk privately without NAT for the Server; NAT is only needed for public AWS services unless you add VPC endpoints. Costs - ECS cluster: $0 (control plane is free). - Worker ECS Service: - If you run the Prefect worker as an ECS Service on Fargate, you pay for that task’s vCPU/GB while it’s up, even when no flows are running. - You can reduce cost by: - Using smaller CPU/memory for the worker. - Considering FARGATE_SPOT for the worker if occasional preemption is acceptable. - Flow runs: - Each flow run is a separate Fargate task billed per vCPU-second and GB-second for its runtime. - Other potential costs: - NAT gateway hourly + data processing, unless you use VPC endpoints. - CloudWatch Logs ingestion/storage. - ECR storage and data transfer. References - Prefect ECS guide: Prefect AWS ECS guide - AWS Fargate pricing: Fargate pricing If you confirm whether your Prefect Server will be behind an internal ALB or exposed directly, I can suggest exact SG rules (source/destination) and whether VPC endpoints could save you NAT costs.

Totally understand the confusion — Prefect’s “ECS worker” and your “flow run tasks” are different things with different billing behaviors. What actually happens - The worker is a long‑lived process that polls your work pool and submits ECS tasks for each flow run. - Each flow run is an ECS Fargate task launched on demand via ecs:RunTask. Cost implications - If you run the worker as an ECS Service on Fargate, you’ll pay for that worker task 24/7 (baseline cost), plus the cost of each flow-run task while it runs. - If you run the worker on your EC2 instance (your current setup), you only pay Fargate for the flow-run tasks when they’re running. No ECS baseline cost. So, if your goal is “pay only when flows run,” do NOT host the worker on Fargate. Keep the worker on your EC2 box and use ECS only for the flow runs. That’s a common and cost‑efficient pattern. Security groups (quick recap) - Prefect Server (on EC2): allow inbound 4200 only from the sources that need it (your worker and flow-run tasks). You don’t need inbound rules on ECS tasks; they just make outbound calls. - ECS worker/tasks: need outbound to your Prefect Server API URL and AWS services (ECR/CloudWatch/STS). Use NAT gateway or VPC endpoints. Decision guide - Pay only during runs: - Keep worker on EC2 (no ECS Service) - Create an ECS work pool in Prefect - Worker on EC2 uses AWS permissions to RunTask on the ECS cluster - Prefer all-in-ECS: - Create ONE ECS Service for the worker (this incurs baseline Fargate cost) - Flow runs still launch as on-demand Fargate tasks Notes - PREFECT_API_URL must include /api, e.g. http(s)//&lt;host or lb&gt;4200/api - ECS control plane/cluster is free; you pay for running tasks (worker if on Fargate, and flow runs), plus NAT/VPC endpoints, CloudWatch Logs, ECR. Docs - Prefect ECS guide: Prefect AWS ECS guide - Fargate pricing: AWS Fargate pricing If you confirm whether you want to keep the worker on EC2 or move it to ECS anyway, I can give you the exact setup (roles, SGs, and work pool variables) for that path.

Perfect—that’s a great, cost‑efficient setup. Here’s exactly how to keep the Prefect worker on your EC2 box and use ECS Fargate only for flow runs. High‑level - No ECS Service is needed. - Your EC2-hosted worker will poll your ECS work pool and call ecs:RunTask to launch Fargate tasks for each flow run. - You’ll pay Fargate only when flow-run tasks are running (plus NAT/VPC endpoints, logs, ECR, etc.). Prereqs your cloud engineer should deliver - ECS cluster name (ap-southeast-1) - Private subnet IDs for Fargate tasks - Security group ID for Fargate tasks - CloudWatch Logs group(s) for flow logs (e.g., /prefect/flows) - IAM roles: - Flow task execution role ARN (ECS execution) - Flow task role ARN (runtime permissions for your flow code) - EC2 instance profile role for the worker with: - ecs:RunTask, ecs:StopTask, ecs:DescribeTasks, ecs:DescribeTaskDefinition, ecs:RegisterTaskDefinition, ecs:DeregisterTaskDefinition, ecs:DescribeClusters - iam:PassRole on the two ARNs above - Prefect Server URL reachable from ECS tasks (private ALB/NLB recommended) - You’ll set PREFECT_API_URL to http(s)//&lt;your server or lb&gt;4200/api Step 1) Create an ECS work pool

prefect work-pool create "ecs-pool" --type ecs

Step 2) Export the default ECS base job template

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

Step 3) Edit ecs-template.json variables - Open ecs-template.json and fill the “variables” section to match your AWS environment. Example (fill in <>):

{
  "job_configuration": { ... }, 
  "variables": {
    "cluster": "arn:aws:ecs:ap-southeast-1:<account-id>:cluster/<your-ecs-cluster>",
    "launch_type": "FARGATE",
    "container_name": "prefect-task",
    "image": "<your-flow-image-uri-or-public-image>",
    "cpu": 512,
    "memory": 1024,
    "execution_role_arn": "arn:aws:iam::<account-id>:role/<flow-task-execution-role>",
    "task_role_arn": "arn:aws:iam::<account-id>:role/<flow-task-role>",
    "vpc_id": "<your-vpc-id>",
    "network_configuration": {
      "awsvpcConfiguration": {
        "subnets": ["subnet-aaaa", "subnet-bbbb"],
        "securityGroups": ["sg-xxxxxx"],
        "assignPublicIp": "DISABLED"
      }
    },
    "configure_cloudwatch_logs": true,
    "cloudwatch_logs_prefix": "prefect",
    "cloudwatch_logs_options": {
      "awslogs-group": "/prefect/flows",
      "awslogs-region": "ap-southeast-1",
      "awslogs-create-group": "true",
      "awslogs-stream-prefix": "flows"
    },
    "stream_output": true,
    "task_start_timeout_seconds": 600,
    "task_watch_poll_interval": 5,
    "auto_deregister_task_definition": true
  }
}

Notes: - Use your private subnets and an SG that allows outbound internet or VPC endpoints for ECR/Logs/STS. - If your flow image is in private ECR, make sure the execution role has ECR read and the network has NAT or ECR VPC endpoints. Step 4) Apply the base job template to the pool

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

Step 5) Start the worker on your EC2 host - Ensure the EC2 instance has the instance profile role with ECS permissions and iam:PassRole. - Set your Prefect API URL (include /api):

export PREFECT_API_URL="http://<your-server-or-internal-lb>:4200/api"
prefect worker start --pool ecs-pool --name ec2-ecs-worker

Step 6) Deploy your flows to this pool Option A: In Python

from prefect import flow

@flow
def my_flow():
    print("hello from ECS")

if __name__ == "__main__":
    from prefect.flows import Flow
    # If your code is in a repo:
    Flow.from_source(
        "<https://github.com/<owner>/<repo>>",
        "path/to/flow.py:my_flow",
    ).deploy(
        name="my-flow-ecs",
        work_pool_name="ecs-pool",
        # Optionally set an image for this deployment; otherwise use the pool default
        image="<your-flow-image-uri>",
    )

Option B: CLI from your project root (if you prefer CLI)

- Run prefect deploy from your project folder with your entrypoint. - You can set the work pool during the deploy flow or update the deployment to use ecs-pool. - If you want, I can provide the exact CLI flags once you confirm your project layout. Security group recap - Prefect Server (EC2): allow inbound 4200 from the ECS tasks’ SG (or via an internal LB). Do not open ECS tasks to inbound; they only need outbound. - ECS tasks: outbound to Prefect Server, ECR, CloudWatch Logs, STS. Use NAT or VPC endpoints. Costs - No ECS Service = no 24/7 Fargate baseline. You pay for: - Each flow-run Fargate task while it runs - NAT or VPC endpoints, CloudWatch Logs ingestion/storage, ECR storage/transfer Docs - Prefect AWS ECS guide: Prefect AWS ECS guide - Workers and Work Pools overview: Workers and Work Pools - Task execution role vs task role: ECS task execution role docs Want me to generate an ecs-template.json tailored to your exact ARNs/subnets/SGs? If you share: - ECS cluster name/ARN - VPC ID, subnet IDs, SG ID - Flow task execution role ARN and task role ARN - CloudWatch log group name I’ll fill it in for you.

Mostly yes — you can do nearly all of the configuration in the Prefect UI, with two important exceptions: - You still need to start the worker process on your EC2 host (CLI or a service like systemd). - You still need to build/push your flow image(s) to ECR (outside Prefect). Here’s the “UI-first” path to keep the worker on EC2 and use ECS only for flow runs: What you’ll do in the Prefect UI 1) Create an ECS work pool - UI: Work Pools -> New -> Type: ECS -> Name it (e.g., ecs-pool). 2) Configure the pool’s Base Job Variables - Open your new pool -> Settings -> Base Job Variables and fill: - cluster: your ECS cluster name or ARN - launch_type: FARGATE - image: your flow image (ECR URI or public image) - cpu / memory: e.g., 512 / 1024 (adjust as needed per flow) - execution_role_arn: ARN of your flow task execution role - task_role_arn: ARN of your flow task role (what your flow code needs) - network_configuration.awsvpcConfiguration: - subnets: [private subnet IDs] - securityGroups: [SG for tasks] - assignPublicIp: DISABLED (recommended with private subnets) - configure_cloudwatch_logs: true - cloudwatch_logs_options: - awslogs-group: /prefect/flows - awslogs-region: ap-southeast-1 - awslogs-create-group: true - awslogs-stream-prefix: flows - stream_output: true - auto_deregister_task_definition: true - Leave aws_credentials empty — your EC2 worker will use its instance profile to call ECS. The flow tasks will assume their task role automatically. Important: In the work pool page, do NOT click “Provision infrastructure” for ECS — that creates a long‑running ECS Service for the worker (which you don’t want, and it costs money). You’re keeping the worker on EC2. What you’ll do on your EC2 host (outside the UI) 1) Ensure IAM on the EC2 instance profile - Allow: ecs:RunTask, ecs:StopTask, ecs:Describe*, ecs:RegisterTaskDefinition, ecs:DeregisterTaskDefinition - Allow: iam:PassRole on your flow task execution role and flow task role ARNs 2) Point the worker to your Server and start it

export PREFECT_API_URL="http://<your-server-or-internal-lb>:4200/api"
prefect worker start --pool ecs-pool --name ec2-ecs-worker

Deploy your flows - You can create deployments via code or CLI; after that, you can manage schedules/parameters in the UI. - Example (from code):

from prefect import flow

@flow
def my_flow():
    print("hello from ECS")

if __name__ == "__main__":
    from prefect.flows import Flow
    Flow.from_source(
        "<https://github.com/<owner>/<repo>>",
        "path/to/flow.py:my_flow",
    ).deploy(
        name="my-flow-ecs",
        work_pool_name="ecs-pool",
        image="<your-ecr-image-uri>",  # or rely on pool default
    )

Networking reminder - No inbound rules needed on ECS tasks. - Prefect Server SG must allow inbound 4200 from the ECS tasks (or an internal ALB SG). - Tasks need outbound to Prefect Server and AWS services (ECR/CloudWatch/STS) via NAT or VPC endpoints. Docs - Prefect AWS ECS guide - Workers and Work Pools - ECS task execution role If you share your cluster name/ARN, subnets, SG, and the two role ARNs, I can fill in the exact Base Job Variables you’ll paste into the UI.

Great — here’s the minimal, no-surprises ticket you can give your cloud engineer to keep the worker on EC2 and use ECS Fargate only for flow runs. No ECS Service is needed. What to provision (minimal) - ECS cluster: already created (confirm name/ARN). - Networking for Fargate tasks: - Private subnet IDs (in your VPC) - One security group for tasks (no inbound needed; outbound allowed) - Ensure tasks can reach: - Prefect Server API on your EC2 host or internal ALB (port 4200) - AWS services: ECR, CloudWatch Logs, STS (via NAT or VPC endpoints) - IAM roles: - Flow task execution role (for pulling images + logs) - Attach AWS managed AmazonECSTaskExecutionRolePolicy - If using private ECR: ECR read permissions - CloudWatch Logs write permissions - Either pre-create the log group or add logs:CreateLogGroup - Flow task role (runtime perms for flow code) - Least-privilege AWS access your flows need (can be empty if not needed yet) - EC2 instance profile (for your worker host) - ecs:RunTask, ecs:StopTask, ecs:Describe*, ecs:RegisterTaskDefinition, ecs:DeregisterTaskDefinition - iam:PassRole to the two ARNs above (execution + task roles) - CloudWatch Logs: - Create a log group for flows (e.g., /prefect/flows), OR allow CreateLogGroup in the execution role - Prefect Server access: - If using an internal ALB/NLB in front of Server, open the Server’s SG to the ECS tasks’ SG on port 4200 - If exposing the EC2 host directly, open its SG on port 4200 to the ECS tasks’ SG - You will set PREFECT_API_URL to http(s)//&lt;server or lb&gt;4200/api Do NOT create - No ECS Service for Prefect. We’re not running the worker on ECS. Please return these values to me - ECS cluster name/ARN - Subnet IDs (list) - Security group ID for tasks - Flow task execution role ARN - Flow task role ARN - CloudWatch Logs group name (if pre-created) - Prefect Server URL I should use for PREFECT_API_URL What I’ll configure in Prefect (UI) - Create an ECS work pool in the Prefect UI - Paste Base Job Variables like:

{
  "cluster": "arn:aws:ecs:ap-southeast-1:<account-id>:cluster/<your-cluster>",
  "launch_type": "FARGATE",
  "container_name": "prefect-task",
  "image": "<your-ecr-image-or-public-image>",
  "cpu": 512,
  "memory": 1024,
  "execution_role_arn": "arn:aws:iam::<account-id>:role/<flow-task-exec-role>",
  "task_role_arn": "arn:aws:iam::<account-id>:role/<flow-task-role>",
  "network_configuration": {
    "awsvpcConfiguration": {
      "subnets": [
        "subnet-aaaa",
        "subnet-bbbb"
      ],
      "securityGroups": [
        "sg-xxxxxx"
      ],
      "assignPublicIp": "DISABLED"
    }
  },
  "configure_cloudwatch_logs": true,
  "cloudwatch_logs_options": {
    "awslogs-group": "/prefect/flows",
    "awslogs-region": "ap-southeast-1",
    "awslogs-create-group": "true",
    "awslogs-stream-prefix": "flows"
  },
  "stream_output": true,
  "auto_deregister_task_definition": true
}

EC2 worker startup (what I’ll do) - Ensure the EC2 instance profile has the ECS + iam:PassRole permissions - Start the worker pointing at the pool:

export PREFECT_API_URL="http://<your-server-or-internal-lb>:4200/api"
prefect worker start --pool ecs-pool --name ec2-ecs-worker

Cost reminder - No ECS Service baseline cost. You pay Fargate only when flow-run tasks are running (plus NAT/VPC endpoints, CloudWatch Logs, ECR). References - Prefect ECS guide: Prefect AWS ECS guide - Workers and Work Pools: Workers and Work Pools - ECS task execution role: AWS docs: task execution role If you want, I can turn this into a ready-to-send ticket with placeholders for your account ID/ARNs—just share your cluster name and whether you’re using an internal ALB for the Server.

Short answer you can send to your engineer: - We don’t have a fixed ECS task definition. Prefect’s ECS worker will register the task definition at run time for each flow. Please create the ECS cluster and the infra below and share the ARNs/IDs back so I can configure the Prefect ECS work pool. What to ask your engineer to provision (ECS + IAM + networking): - ECS - ECS cluster in ap-southeast-1 (e.g., name: prefect-flows) - Fargate capacity is preferred (simpler ops) - Optional but nice: CloudWatch log group (e.g., /ecs/prefect) with retention - ECR repository for our flow image (e.g., 123456789012.dkr.ecr.ap-southeast-1.amazonaws.com/prefect-flows) - Networking - VPC and private subnet IDs for tasks (recommend at least 2 subnets across AZs) - Security group for ECS tasks with: - Egress to the Prefect API on our EC2 host (port 4200 by default) and any other services our flows need (S3, DBs, APIs, etc.) - Update the EC2 host’s security group (where Prefect Server runs) to allow inbound from the ECS task SG to port 4200 - If tasks are in private subnets, ensure NAT for outbound internet (to pull images from ECR and reach any external services) - IAM - Task execution role (e.g., arnawsiam:&lt;acct&gt;role/ecsTaskExecutionRole) with AmazonECSTaskExecutionRolePolicy attached for pulling images and sending logs - Task role (e.g., arnawsiam:&lt;acct&gt;role/prefect-task-role) with permissions our flows need (S3/Secrets Manager/etc.). We can refine this as we define flows. - The IAM principal used by the Prefect worker (your EC2 instance role or an AWS key) must be allowed to: - ecs:RunTask - ecs:DescribeTasks, ecs:DescribeTaskDefinition - ecs:RegisterTaskDefinition (if we let Prefect auto-create task defs) - iam:PassRole on the task role and execution role ARNs Notes about the “task definition name” - You do not need to provide one up front. In Prefect 3.x with an ECS work pool, the worker will register a task definition automatically per flow run based on your pool’s template. - If your org requires a pre-created family, ask them to create a Fargate-compatible family (networkMode=awsvpc) and share the family name/ARN with you. We can point the pool at it, but it’s optional. What I’ll need back from the engineer - ECS cluster name/ARN - Private subnet IDs (and whether assignPublicIp should be disabled or enabled) - ECS task security group ID - Task execution role ARN - Task role ARN - CloudWatch log group name (if pre-created) - ECR repo URI for the image Your next steps in Prefect - In the Prefect UI, create a Work Pool of type ECS and fill in: - Cluster - Subnets and Security Groups - Launch type FARGATE (and platform version LATEST) - Task role ARN and Execution role ARN - CPU/Memory defaults for flow runs - Image (point to the ECR image you’ll build) - Log configuration (CloudWatch log group) - Start a Prefect ECS worker on your EC2 host and point it at that pool. Make sure the worker process has AWS credentials with the ECS permissions noted above. - Deploy your flows to that ECS work pool. You can use Prefect’s deployment tooling; Prefect will run each flow as an ECS task using the pool template. Helpful docs - ECS guide: Run Prefect on AWS ECS (3.x) - Creating deployments: Create deployments in Prefect 3.x A couple of clarifications to help me tailor the pool template for you: - Will you run tasks on Fargate (recommended) or EC2-backed ECS? - Do your flows need access to specific AWS services (S3, Secrets Manager, RDS, etc.) so we can scope the task role? - Do you want tasks to stay private-only inside the VPC, or can they have public IPs? - What default CPU/Memory should we use per flow run (e.g., 1 vCPU/2GB)?

Great — thanks for the details. Since you’re using an ECS cluster with EC2 launch type, here’s exactly what to send back to your engineer and what you should set in Prefect. Copy/paste reply to your engineer - We don’t have a fixed ECS task definition. Prefect’s ECS worker will register task definitions dynamically at run time for each flow. - Please provision: - ECS cluster (EC2 launch type) in ap-southeast-1, with at least one container instance joined to the cluster (ecsInstanceRole attached). - VPC subnets (prefer private subnets in at least 2 AZs). - Security group for ECS tasks that can: - Reach our Prefect Server on port 4200 on the EC2 host - Reach the RDS instance on port 5432 - Egress to the internet (via NAT) to pull images from ECR and send logs to CloudWatch - Security group updates: - Prefect Server EC2 SG: allow inbound from the ECS tasks SG to port 4200 - RDS SG: allow inbound from the ECS tasks SG to port 5432 - CloudWatch log group for ECS tasks (e.g., /ecs/prefect) with retention - ECR repository for our flow image - IAM roles: - Task execution role with AmazonECSTaskExecutionRolePolicy (for ECR pulls and logs) - Task role for the flow containers (least-privileged; we only need app-level access — DB creds are handled in Prefect) - The credentials used by the Prefect worker must be allowed to: - ecs:RunTask, ecs:DescribeTasks, ecs:RegisterTaskDefinition, ecs:DescribeTaskDefinition - iam:PassRole on the task role and execution role - Please share back: - ECS cluster name/ARN - Subnet IDs - ECS task security group ID - Task execution role ARN - Task role ARN - CloudWatch log group name - ECR repo URI Recommended defaults for now (POC) - Launch type: EC2 - Network mode: awsvpc - Public IPs: keep private-only (don’t assign public IPs); ensure NAT for outbound - CPU/Memory: cpu 256, memory 512 (we’ll tune for prod later) What you need to do in Prefect 1) Ensure your ECS tasks can reach your Prefect API - Because Prefect Server runs on a single EC2 instance, make sure PREFECT_API_URL that the worker uses points to an address the ECS tasks can reach (not localhost). - Example: http//&lt;your EC2 private IP or DNS&gt;4200/api - Make sure the ECS tasks SG can reach port 4200 on that host. 2) Create an ECS work pool (in the Prefect UI) - Type: ECS - Launch type: EC2 - Cluster: set to the cluster name from your engineer - Networking: add the private subnets and the ECS task SG; leave public IPs disabled - Roles: set Task Role ARN and Execution Role ARN - Logs: set the CloudWatch log group - Image: set your ECR image (you can start with a simple image that has your flow deps) - Defaults: CPU 256 / Memory 512 for POC 3) Start a Prefect worker on your EC2 host (where Prefect Server runs) - Run it with AWS credentials that have the ECS permissions listed above. - The worker will register task definitions and run ECS tasks for each flow. RDS access with credentials stored in Prefect - Keep using Prefect’s Secret block (or Variables) for DB creds; do not bake them into the image or task role. - Example in your flow:

from prefect.blocks.system import Secret

dsn = Secret.load("rds-postgres-dsn").get()
# Use dsn in your DB client

- Confirm the ECS tasks’ SG is allowed to connect to the RDS SG on port 5432. Docs - ECS guide: Run Prefect on AWS ECS (3.x) - Deployments: Create deployments in Prefect 3.x Open questions to confirm - What hostname or private IP should we use for PREFECT_API_URL so that ECS tasks can reach the Prefect Server? - Do you already have a base ECR image for the POC, or would you like a minimal Dockerfile to start?

Totally fair question. Prefect doesn’t need long‑lived AWS access keys if the worker (or your flow tasks) run on AWS compute that has an IAM role attached. The AWS SDK inside the container automatically picks up temporary credentials from the instance/task metadata service. How this works, depending on where the Prefect worker runs: - Worker on EC2 (your current setup): Attach an instance profile (IAM role) to the EC2 host. The worker process uses those temporary credentials via IMDSv2 to call ECS APIs (RunTask, RegisterTaskDefinition, etc.). No static keys needed. - Worker on ECS Fargate: Attach an IAM task role to the worker task definition. The worker container receives temporary credentials via the task metadata endpoint. Again, no static keys needed. What IAM the worker needs - Permissions to operate ECS: - ecs:RunTask - ecs:RegisterTaskDefinition - ecs:DescribeTasks - ecs:DescribeTaskDefinition - Permission to pass the roles used by your flow tasks: - iam:PassRole on the task role ARN and execution role ARN you configure in the ECS work pool - Optional reads/listing for your cluster if you reference by name - The ECR/CloudWatch permissions for pulling images and logs are handled by the ECS Task Execution Role on the flow task, not the worker What about your flow containers - Each flow run is its own ECS task. Attach a Task Role to that task to grant AWS access (if needed). The container gets temporary creds via the metadata endpoint—no keys. - In your case you’re connecting to RDS with a username/password stored in Prefect. That’s fine. The ECS task’s security group just needs to reach the RDS SG on 5432. So “without AWS access keys” really means “with short‑lived credentials from an IAM role on the compute that is running the process”: - EC2 instance profile for a worker on EC2 - ECS task role for a worker running on Fargate - And a separate task role for each flow task (least privilege) If you want, I can draft: - The minimal IAM policy for the worker role (including the iam:PassRole condition to specific ARNs) - The task role policy for your flow tasks (if/when they need AWS access) - The exact worker start command and environment variables needed (e.g., PREFECT_API_URL) for your setup Docs for reference: - ECS guide: Run Prefect on AWS ECS (3.x)

Short answer: you do NOT put AWS keys into the Prefect ECS work pool. The work pool just stores config (cluster, subnets, roles, etc.). The Prefect worker process uses whatever AWS credentials are available on the machine it runs on. In your case, run the worker on your EC2 instance and attach an IAM instance profile (role) to that EC2. The worker will get temporary creds from IMDS automatically. Minimum IAM permissions for the EC2 instance role running the Prefect worker Attach a policy like this to the EC2 instance profile role:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "ECSControlPlane",
      "Effect": "Allow",
      "Action": [
        "ecs:RunTask",
        "ecs:RegisterTaskDefinition",
        "ecs:DescribeTasks",
        "ecs:DescribeTaskDefinition",
        "ecs:DescribeClusters",
        "ecs:ListClusters",
        "ecs:ListTaskDefinitions"
      ],
      "Resource": "*"
    },
    {
      "Sid": "AllowPassingEcsTaskRoles",
      "Effect": "Allow",
      "Action": "iam:PassRole",
      "Resource": [
        "arn:aws:iam::<ACCOUNT_ID>:role/prefect-ecs-task-role",
        "arn:aws:iam::<ACCOUNT_ID>:role/ecsTaskExecutionRole"
      ],
      "Condition": {
        "StringEquals": {
          "iam:PassedToService": "<http://ecs-tasks.amazonaws.com|ecs-tasks.amazonaws.com>"
        }
      }
    }
  ]
}

Notes - Replace the two role ARNs with the actual Task Role and Task Execution Role you’ll use for your flow tasks. - The iam:PassRole permission is critical because the worker: - Registers task definitions that reference those roles - Runs tasks that must assume those roles - You can pare back the List* permissions if desired; they’re convenient for validation but not strictly required at runtime. - You do not need ECR or CloudWatch Logs permissions on the worker role; those are handled by the ECS Task Execution Role attached to each flow task. Trust policy for the EC2 instance role (so the instance can assume it)

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Service": "<http://ec2.amazonaws.com|ec2.amazonaws.com>"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}

Where to put these in Prefect - In the Prefect UI, create an ECS work pool and reference: - The cluster name - Subnet IDs and Security Group for tasks - The Task Role ARN and Task Execution Role ARN (these are the roles your flow tasks will use) - Do not put AWS keys in the work pool. - Start the Prefect worker on your EC2 instance. The worker will use the EC2 instance role automatically. If you ever run the worker on ECS/Fargate instead of EC2 - Use the same permissions as above, but attach them to the worker task’s role (trust policy principal becomes ecs-tasks.amazonaws.com). Docs - Run Prefect on AWS ECS (3.x) If you share the exact ARNs for your task role and execution role, I can tailor the iam:PassRole statement precisely and suggest optional resource-level restrictions.

Short answer: yes — the EC2 instance that runs your Prefect ECS worker needs ECS permissions. Prefect Server itself does not. Since you’re running both on the same EC2, attach the permissions to that instance profile. There are 3 (often 4) IAM roles to think about: 1) Instance profile on the EC2 that runs the Prefect worker (your host) - What it does: Calls ECS APIs to register task definitions and run/stop tasks. - Needs: - ecs:RunTask - ecs:RegisterTaskDefinition - ecs:DescribeTasks, ecs:DescribeTaskDefinition, ecs:DescribeClusters, ecs:ListTaskDefinitions - ecs:StopTask (so the worker can cancel) - iam:PassRole for BOTH the ECS task execution role and the task role (see #2 and #3) - Example minimal policy for the worker host:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "ECSControl",
      "Effect": "Allow",
      "Action": [
        "ecs:RunTask",
        "ecs:RegisterTaskDefinition",
        "ecs:DescribeTasks",
        "ecs:StopTask",
        "ecs:DescribeTaskDefinition",
        "ecs:ListTaskDefinitions",
        "ecs:DescribeClusters"
      ],
      "Resource": "*"
    },
    {
      "Sid": "PassRolesToECS",
      "Effect": "Allow",
      "Action": "iam:PassRole",
      "Resource": [
        "arn:aws:iam::<account-id>:role/<ecs-task-execution-role>",
        "arn:aws:iam::<account-id>:role/<ecs-task-role>"
      ],
      "Condition": {
        "StringLike": {
          "iam:PassedToService": "<http://ecs-tasks.amazonaws.com|ecs-tasks.amazonaws.com>"
        }
      }
    }
  ]
}

2) ECS task execution role (used by ECS to pull images, write logs) - Attach AWS managed policy: AmazonECSTaskExecutionRolePolicy - This gives ECR and CloudWatch Logs access needed to pull your image and stream logs. - Docs: AWS: Task execution role 3) ECS task role (your flow’s application role) - What your flow actually uses inside the container. - Grant only what your code needs (e.g., S3 access). For RDS with username/password, you may not need any AWS perms here. - Note: Prefect-stored DB credentials are fine; just ensure the task is in the right subnets/SGs to reach RDS. 4) ECS container instance role (only for EC2 launch type capacity hosts) - If you’re running your own ECS cluster with EC2 container instances, those instances need the ecsInstanceRole with the AWS managed policy AmazonEC2ContainerServiceforEC2Role so the ECS agent can register with the cluster. - Docs: AWS: Container instance IAM role Notes and common gotchas - The worker host needs iam:PassRole for both the execution role and the task role ARNs — this is the most common missing permission. - The worker host does NOT need ECR or CloudWatch Logs permissions; the execution role handles those. - Ensure you actually have EC2 capacity registered in your ECS cluster (EC2 launch type) with the correct instance role (#4). The worker just submits tasks — ECS must have instances to place them on. - For RDS access: place tasks in subnets/SGs that can reach your RDS SG; IAM isn’t required if you’re using password auth. - Prefect 3 ECS guide: Prefect 3: ECS worker guide Questions to confirm so I can tailor this exactly: - Do you already have an ECS cluster with EC2 container instances registered, or are you planning to register your Prefect EC2 host as a container instance too? - Are your images in ECR (same account/region as ap-southeast-1)? - Beyond RDS, will flows need access to S3/Secrets Manager/etc. from inside the task?

@Marvin what if my cloud engineer does not allow anyone else to run ecs task, or provide ecs run related permissions to anyone else. He creates the cluster and we have to give him the ecs task.

Got it — if your cloud engineer won’t let your team/principal run ECS tasks, there are two workable patterns: Option A (recommended): They own the worker role and lock it down - Have your engineer: - Create the ECS cluster, EC2 capacity, and the ECS task definition for your flow image. - Create a very restricted IAM role that ONLY allows

ecs:RunTask

against that task definition on that cluster, plus read-only describes and

iam:PassRole

for the two ECS roles (execution role and task role). - Run the Prefect ECS worker (as a long‑running service or on your EC2) using that locked‑down role. - You provide: - The ECR image URI and the ECS task definition you want (CPU/mem, container name, env/logging, subnets/SGs). - The Prefect work pool name and server URL (and API key if using Prefect Cloud). - Configure the Prefect ECS work pool to use the existing task definition (no re-registering). The worker will only supply container overrides (command/env) at run time. - Prefect will then just queue work; the worker (running under their restricted role) will call

RunTask

. Minimal worker IAM policy (tight scope, no task definition registration):

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "RunOnlyThisTaskOnThisCluster",
      "Effect": "Allow",
      "Action": "ecs:RunTask",
      "Resource": "arn:aws:ecs:<region>:<account-id>:task-definition/<family-or-arn>",
      "Condition": {
        "ArnEquals": {
          "ecs:cluster": "arn:aws:ecs:<region>:<account-id>:cluster/<cluster-name>"
        }
      }
    },
    {
      "Sid": "DescribeForStatus",
      "Effect": "Allow",
      "Action": [
        "ecs:DescribeTasks",
        "ecs:DescribeTaskDefinition",
        "ecs:DescribeClusters"
      ],
      "Resource": "*"
    },
    {
      "Sid": "OptionalStopForCancellations",
      "Effect": "Allow",
      "Action": "ecs:StopTask",
      "Resource": "*",
      "Condition": {
        "ArnEquals": {
          "ecs:cluster": "arn:aws:ecs:<region>:<account-id>:cluster/<cluster-name>"
        }
      }
    },
    {
      "Sid": "PassOnlyTheseRolesToECS",
      "Effect": "Allow",
      "Action": "iam:PassRole",
      "Resource": [
        "arn:aws:iam::<account-id>:role/<ecs-task-execution-role>",
        "arn:aws:iam::<account-id>:role/<ecs-task-role>"
      ],
      "Condition": {
        "StringLike": {
          "iam:PassedToService": "<http://ecs-tasks.amazonaws.com|ecs-tasks.amazonaws.com>"
        }
      }
    }
  ]
}

- No

ecs:RegisterTaskDefinition

needed if you pre-create the task definition. - You can even omit

ecs:StopTask

if they don’t want Prefect to cancel tasks; just know flow cancellations won’t stop running containers. - The ECR pull and CloudWatch Logs access are handled by the ECS task execution role (attach AWS managed

AmazonECSTaskExecutionRolePolicy

to that role). Option B: If they will not grant

ecs:RunTask

to any worker at all - Then Prefect cannot dispatch ECS tasks. In that case, either: - Run flows with a non‑ECS work pool (Process or Docker) on your EC2 host, or - Let them schedule ECS tasks outside Prefect (EventBridge/Cron), but Prefect won’t be orchestrating those runs. Relevant docs - Prefect 3 ECS worker guide: Prefect 3: ECS worker guide - AWS: Task execution role: AWS: Task execution role - AWS: ECS IAM actions/resources: AWS: ECS IAM actions, resources, and condition keys Clarifying question to proceed:

- Can your engineer allow a role that has only

ecs:RunTask

(restricted to your cluster + task definition) and

iam:PassRole

for the specific execution/task roles? If yes, I’ll help you fill out the exact work pool base job template to use the pre-created task definition so no registrations happen.

You’re right: in Option B (no one outside the platform team can call ECS RunTask), Prefect cannot autoscale by provisioning ECS tasks. You’re limited to whatever compute is running your workers. If you still want elastic capacity without granting

ecs:RunTask

, here are workable patterns: 1) EventBridge “indirection” (no ECS perms for Prefect) - Flow: Prefect worker → events:PutEvents → EventBridge rule → ECS RunTask (using a target role owned by your engineer). - Prefect only needs:

{
  "Effect": "Allow",
  "Action": "events:PutEvents",
  "Resource": "arn:aws:events:ap-southeast-1:<account-id>:event-bus/<bus-name>"
}

- Your engineer configures: - EventBridge rule that targets ECS RunTask for your cluster + task definition. - A target role that has

ecs:RunTask

+

iam:PassRole

for the task execution + task roles. - Result: Prefect triggers tasks indirectly; scaling is handled by ECS EC2 capacity. 2) SNS/Lambda “run-task proxy” - Flow: Prefect worker → sns:Publish → Lambda → ecs:RunTask. - Prefect only needs:

{
  "Effect": "Allow",
  "Action": "sns:Publish",
  "Resource": "arn:aws:sns:ap-southeast-1:<account-id>:<topic>"
}

- Lambda’s role (owned by your engineer) has

ecs:RunTask

+

iam:PassRole

scoped to your cluster/task def. - Result: No ECS perms on Prefect side; autoscaling via ECS remains possible. 3) Engineer-owned ECS worker - They run the Prefect ECS worker under a tightly-scoped role that can

RunTask

. You provide pool config; they control IAM and scale by running more workers or increasing service count. Prefect can still schedule many runs; ECS provides elasticity. 4) Non‑ECS workers with EC2 Auto Scaling - If you must avoid ECS entirely, run Process or Docker workers on an EC2 Auto Scaling Group. - Use a launch template that starts:

prefect worker start -p <your-work-pool>

- Scale the ASG via CPU or a small scaler that publishes a “queue backlog” custom metric. - You still get some elasticity, but it’s bounded by your ASG capacity, not ECS tasks. If none of the indirection patterns (1 or 2) are acceptable, then yes, you’re restricted to the capacity where your workers run. Want me to draft the exact IAM, EventBridge target role, and the Prefect work pool config for Option 1 (EventBridge) or Option 2 (SNS/Lambda)?

Yes — that’s a great approach, and it’s the recommended way to keep control centralized. If your cloud engineer: - Creates an IAM role with tightly-scoped ECS permissions - Attaches it as the EC2 instance profile on the box running your Prefect worker …then you do not need any access keys. The worker will pick up temporary creds from the instance metadata service (IMDSv2), and your engineer retains full control of what the worker is allowed to do. What your engineer sets up - ECS cluster and EC2 capacity (EC2 launch type) - Pre-created ECS task definition for your flow image - Task execution role (with AmazonECSTaskExecutionRolePolicy) - Task role (what your flow needs; can be minimal if you only use RDS with a password) - Container instance role on the ECS capacity hosts (AmazonEC2ContainerServiceforEC2Role), NOT on your Prefect worker host unless that host is also an ECS container instance - Instance profile on your Prefect worker EC2 with a minimal, locked-down policy, for example:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "RunOnlyThisTaskOnThisCluster",
      "Effect": "Allow",
      "Action": "ecs:RunTask",
      "Resource": "arn:aws:ecs:<region>:<account-id>:task-definition/<family-or-arn>",
      "Condition": {
        "ArnEquals": {
          "ecs:cluster": "arn:aws:ecs:<region>:<account-id>:cluster/<cluster-name>"
        }
      }
    },
    {
      "Sid": "DescribeForStatus",
      "Effect": "Allow",
      "Action": [
        "ecs:DescribeTasks",
        "ecs:DescribeTaskDefinition",
        "ecs:DescribeClusters"
      ],
      "Resource": "*"
    },
    {
      "Sid": "OptionalStopForCancellations",
      "Effect": "Allow",
      "Action": "ecs:StopTask",
      "Resource": "*",
      "Condition": {
        "ArnEquals": {
          "ecs:cluster": "arn:aws:ecs:<region>:<account-id>:cluster/<cluster-name>"
        }
      }
    },
    {
      "Sid": "PassOnlyTheseRolesToECS",
      "Effect": "Allow",
      "Action": "iam:PassRole",
      "Resource": [
        "arn:aws:iam::<account-id>:role/<ecs-task-execution-role>",
        "arn:aws:iam::<account-id>:role/<ecs-task-role>"
      ],
      "Condition": {
        "StringLike": {
          "iam:PassedToService": "<http://ecs-tasks.amazonaws.com|ecs-tasks.amazonaws.com>"
        }
      }
    }
  ]
}

- Note: No

ecs:RegisterTaskDefinition

permission is needed if they pre-create the task definition. What you configure in Prefect - Create an ECS work pool and set the base job template to use: - The existing ECS cluster name/ARN - The pre-created task definition ARN (so the worker does not register new task defs) - Network settings (subnets/security groups) that can reach your RDS - Container name to override, plus optional command/env overrides as needed - Run the worker on that EC2 instance (with the instance profile attached). It will use IMDS credentials automatically. Control boundaries - Your engineer controls: - Which cluster and task definition can be used (via resource-scoped IAM and PassRole) - The task execution and task roles - ECS capacity and scaling - You do not need any static credentials and cannot run arbitrary ECS tasks outside the allowed scope. Docs for reference - Prefect 3 ECS worker guide: Prefect 3: ECS worker guide - AWS: Task execution role: AWS: Task execution role - AWS: Container instance role (EC2 launch type): AWS: Container instance IAM role If you want, I can draft the exact IAM policy with your real ARNs (cluster, task definition, execution/task roles) and a quick checklist for your engineer, plus the work pool base job template fields to fill in.

Yes, that will work — and it keeps infra control with your cloud engineer. How it works - Your engineer attaches an IAM role to your EC2 (instance profile) with tightly scoped ECS permissions. The Prefect worker on that EC2 uses IMDS credentials — no access keys needed. - The Prefect ECS worker submits tasks to ECS. ECS places them on your EC2 container instances and can autoscale via a capacity provider/ASG. - ECR pulls and CloudWatch Logs are handled by the ECS task execution role, not by the Prefect worker’s role. What your engineer should set up - ECS cluster (EC2 launch type) in ap-southeast-1. - EC2 Auto Scaling Group + ECS capacity provider for autoscaling. - ECR repo and your flow images. - Task execution role with AmazonECSTaskExecutionRolePolicy (ECR pulls, logs). - Task role for your flow’s app needs. - Either: - Pre-create a task definition and give you the ARN, or - Allow the worker to register task definitions (if they’re okay with ecs:RegisterTaskDefinition). - Instance profile on your EC2 running the Prefect worker with minimum perms: - ecs:RunTask restricted to your cluster + task definition - ecs:DescribeTasks/TaskDefinition/Clusters - ecs:StopTask (optional, for cancellations) - iam:PassRole for the execution role and task role - Note: ECR permissions belong on the execution role, not the worker role. What you do in Prefect - Create an ECS work pool in the UI and set the base job template to: - Cluster name/ARN and launch type EC2 - Subnets and security groups that can reach your RDS - Task execution role ARN and task role ARN - Either reference the pre-created task definition ARN, or supply image/CPU/memory so Prefect can register a task definition - Container name and any command/env overrides - Start a worker on your EC2 (with that instance profile) to poll the pool:

prefect worker start -p <your-ecs-work-pool>

Autoscaling note - Prefect “autoscaling” here means it will submit more ECS tasks as more flow runs queue up. Actual compute scaling comes from ECS capacity providers/ASGs. If you only have a single ECS container instance, there’s nothing for ECS to scale — make sure your engineer configures a capacity provider. - AWS docs: ECS capacity providers and managed scaling Helpful references - Prefect 3 ECS worker guide: Prefect 3: ECS worker guide - AWS: Task execution role (ECR/Logs): Task execution role If you share your cluster ARN, task definition ARN, and the two role ARNs, I can draft the exact IAM policy for the EC2 instance profile and the base job template values to paste into the work pool.

Short answer: yes, you can use Fargate with Prefect 3, and it can be a great fit for bursty, on‑demand flow runs. You’d keep Prefect Server + the ECS worker on your EC2 instance, but the actual flow runs execute as Fargate tasks that scale to zero when idle. When Fargate makes sense - Burst/irregular workloads: pay per task (vCPU+memory per second), zero idle cost - Minimal ops: no ECS EC2 capacity/ASG to manage - Quick scale-out: ECS can launch many Fargate tasks in parallel When EC2 launch type may be cheaper - Steady, high utilization: a well-sized EC2 ASG is often lower cost than Fargate - Special needs: privileged mode, host networking, or custom AMIs (Fargate doesn’t support these) Prefect + Fargate specifics - Prefect ECS worker supports Fargate. In the work pool’s base job template, set: - launch_type: FARGATE (or use capacity providers FARGATE / FARGATE_SPOT) - cluster name/ARN - subnets and security groups (must reach your RDS) - task execution role ARN (ECR pulls + CloudWatch logs) - task role ARN (what your flow needs; for RDS with password, may be minimal) - valid Fargate CPU/memory combo (AWS has specific allowed pairs) - assignPublicIp: ENABLED if using public subnets without NAT; otherwise DISABLED with NAT or VPC endpoints - You can either: - Reference a pre-created task definition (no ecs:RegisterTaskDefinition needed), or - Allow the worker to register task definitions dynamically (requires ecs:RegisterTaskDefinition) IAM differences vs EC2 launch type - You do NOT need the ECS container instance role (that’s only for EC2 capacity hosts) - The worker’s instance profile still needs: - ecs:RunTask restricted to your cluster + task definition (or family) - ecs:DescribeTasks/TaskDefinition/Clusters - ecs:StopTask (optional, for cancellations) - iam:PassRole for the task execution role and the task role - The execution role must have the AWS managed policy AmazonECSTaskExecutionRolePolicy (ECR pulls, logs) Cost notes - Fargate is billed per vCPU-second and GB-second. For always-on/long-running jobs, EC2 is usually cheaper; for intermittent spikes, Fargate is often cheaper overall because you don’t pay for idle capacity. - Consider Fargate Spot for further savings if your flows are retry-safe; tasks can be interrupted. - Pricing varies by region; see AWS Fargate pricing. Networking to RDS - Put Fargate tasks in private subnets with SG rules that allow access to RDS’s SG. - If tasks need internet/ECR/CloudWatch without NAT, set up VPC endpoints (ECR API/DKR, Logs) or enable public IP and use public subnets. References - Prefect 3 ECS worker guide: Prefect 3: ECS worker guide - AWS: Task execution role: AWS: Task execution role - AWS: Fargate capacity providers and scaling: ECS capacity providers If you want to try Fargate, I can: - Draft the minimal IAM for your worker’s instance profile (scoped to your cluster/TD) - Provide the base job template fields for your work pool - Suggest sane CPU/memory combos and networking settings for ap-southeast-1

Awesome — with ECS approved for both Prefect Server and the ECS worker (EC2 launch type), here’s a clean next-step plan you can hand to your cloud team and use yourself. I’m assuming Prefect 3.x. High-level checklist - Networking - Decide VPC/subnets (private for tasks), security groups, and an ALB/NLB for the Server UI/API (port 4200). - Open RDS inbound from the ECS tasks’ SG. - IAM - Create an ECS execution role (standard AmazonECSTaskExecutionRolePolicy) for pulling images and pushing logs. - Create a task role for the Prefect Server task (CW logs access if needed). - Create a worker task role with permissions to run ECS tasks: - ecs:RunTask, ecs:DescribeTasks, ecs:StopTask - iam:PassRole (limited to the taskRoleArn and executionRoleArn used by your flow-run tasks) - logs:CreateLogGroup/Stream, logs:PutLogEvents (if you want CloudWatch log streaming) - Images - Use the Prefect image matching your version (pin to a specific 3.x.y): e.g.

prefecthq/prefect:3.x.y-python3.11

- Your flows should run in a runtime image that includes your dependencies (build into ECR and reference in the ECS work pool template). 1) Bring up Prefect Server as an ECS Service - Task definition: - Container image:

prefecthq/prefect:<your-3.x.y-tag>

- Command:

prefect server start --host 0.0.0.0 --port 4200 --ui

- Port mapping: container 4200 - Env vars: - This one is required for RDS:

PREFECT_API_DATABASE_CONNECTION_URL=postgresql+asyncpg://<user>:<password>@<rds-endpoint>:5432/<db_name>

- Optional (only if you need to override defaults):

PREFECT_SERVER_API_HOST=0.0.0.0
      PREFECT_SERVER_API_PORT=4200

- Execution role: ECS task execution role - Task role: to allow CloudWatch logging if needed - Logs: send to CloudWatch - ALB/NLB: - Target port 4200 to the Server service - Optional TLS on the ALB - Quick health check: - After deploy, verify:

curl http://<load-balancer-dns>:4200/api/health

- It should return OK. Docs: - Server on Docker/ECS - Settings reference 2) Create an ECS work pool (EC2 launch type) Run these locally (or from any machine that can reach your server API). If you’re self-hosting server, set

PREFECT_API_URL

on your shell first so the CLI talks to your server:

export PREFECT_API_URL=http://<load-balancer-dns>:4200/api
prefect work-pool create ecs-ec2-pool --type ecs
prefect work-pool get-default-base-job-template --type ecs > ecs-job-template.json

Edit

ecs-job-template.json

so most defaults are set in the pool (so deployments don’t need to repeat them). Key fields to fill: - job_configuration.task_definition - family: your task definition family name for flow runs (or leave blank and use

task_definition_arn

) - executionRoleArn: arnawsiam:&lt;acct&gt;role/<ecs-execution-role> - containerDefinitions[0].name: a container name (e.g.,

flow-run

) - job_configuration.task_run_request - launchType:

EC2

- cluster: your ECS cluster name or ARN - overrides.taskRoleArn: arnawsiam:&lt;acct&gt;role/<flow-run-task-role> - taskDefinition: either blank (and use family + match_latest_revision_in_family=true) or a specific ARN - job_configuration.network_configuration - subnets: ["subnet-...","subnet-..."] - securityGroups: ["sg-..."] - assignPublicIp: false (if using private subnets) - Optional CloudWatch logs: - configure_cloudwatch_logs: true - cloudwatch_logs_options: e.g., region, logGroup, streamPrefix - Optional: - vpc_id: "vpc-..." - match_latest_revision_in_family: true Save and update:

prefect work-pool update ecs-ec2-pool --base-job-template ecs-job-template.json

Docs: - ECS worker guide 3) Run the Prefect worker as an ECS Service

- Create another ECS Service that runs the Prefect image: - Image:

prefecthq/prefect:<your-3.x.y-tag>

- Command:

prefect worker start --pool ecs-ec2-pool --name ecs-ec2-worker

- Env vars:

PREFECT_API_URL=http://<server-internal-lb-or-service-dns>:4200/api

- Task Role: the “worker task role” described above with ecs:RunTask, iam:PassRole, etc. - Execution Role: standard ECS execution role - Logs: send to CloudWatch 4) Deploy flows to the ECS work pool - Prefer the Prefect 3 pattern where the flow is pulled from source. For example:

from prefect import flow

@flow
def my_flow():
    print("hello from ECS")

if __name__ == "__main__":
    my_flow.from_source(
        source="<https://github.com/<owner>/<repo>>",
        entrypoint="flows/my_flow.py:my_flow",
    ).deploy(
        name="my-flow",
        work_pool_name="ecs-ec2-pool",
        # Only include job vars that change per-deployment;
        # everything else should be set in the pool template
        job_variables={
            "image": "<http://123456789012.dkr.ecr.ap-southeast-1.amazonaws.com/my-runtime:latest|123456789012.dkr.ecr.ap-southeast-1.amazonaws.com/my-runtime:latest>"
        },
    )

- Make sure your runtime image includes your flow’s Python dependencies and access to any private repos/registries you need. Important notes specific to your setup - Database credentials - The Prefect Server’s DB credentials cannot be stored in Prefect itself — the server needs them at startup. Provide them via ECS task definition environment variables or inject from AWS Secrets Manager. - Your flows’ DB credentials can be stored in Prefect (Variables/Secrets) and injected into flow-run tasks via the ECS pool template’s

env

settings. - Networking - Ensure flow-run tasks can reach RDS (open SG/Route). - Ensure the worker service can reach the Prefect Server API endpoint and ECS control plane. - Environments on one host/cluster - Use separate work pools per environment (e.g.,

ecs-ec2-dev

,

ecs-ec2-stage

,

ecs-ec2-prod

) and separate RDS DBs or schemas. - Optionally, create separate ECS services for workers per environment. You can also scope different subnets/SGs if needed. Questions to confirm before I draft exact JSON/task definitions: 1) Will the Prefect Server UI/API be public behind an ALB (TLS), or private only inside the VPC? 2) Do you already have an ECR runtime image for your flows, or should I help you create one? 3) Do you want one ECS worker service per environment (recommended) or a single worker that polls multiple pools? Happy to turn this into concrete ECS task/service definitions once you confirm the above.