Great — here’s a clean, production-ready starting point for running Prefect Server (3.x) in Docker and on ECS (EC2 launch type) with your RDS Postgres. No Redis required. Notes: - Server entrypoint:

prefect server start

(starts API + services + UI). - Database URL must use

postgresql+asyncpg://

. - Expose/listen on 4200; clients/workers will use

PREFECT_API_URL

to reach the server at

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

. Dockerfile (build your Prefect Server image)

# Simple Prefect Server image for Prefect 3.x
FROM python:3.11-slim

ENV PYTHONDONTWRITEBYTECODE=1 \
    PYTHONUNBUFFERED=1 \
    PIP_NO_CACHE_DIR=1

# Install Prefect 3 and Postgres driver
RUN pip install --upgrade pip && \
    pip install "prefect>=3,<4" asyncpg

# Defaults: override via ECS Task env
ENV PREFECT_SERVER_API_HOST=0.0.0.0 \
    PREFECT_SERVER_API_PORT=4200 \
    PREFECT_UI_ENABLED=true \
    PREFECT_API_DATABASE_MIGRATE_ON_START=true

# Prefect Server listens on 4200
EXPOSE 4200

# Start Prefect Server (API + services + UI)
CMD ["prefect", "server", "start", "--host", "0.0.0.0", "--port", "4200"]

Example ECS Task Definition (EC2 launch type) - Uses awsvpc networking - Publishes port 4200 on the host for easy access from your EC2’s SG or an ALB - Pulls the Postgres URL from Secrets Manager (recommended)

{
  "family": "prefect-server",
  "networkMode": "awsvpc",
  "requiresCompatibilities": [
    "EC2"
  ],
  "cpu": "512",
  "memory": "1024",
  "executionRoleArn": "arn:aws:iam::<account-id>:role/ecsTaskExecutionRole",
  "taskRoleArn": "arn:aws:iam::<account-id>:role/prefectServerTaskRole",
  "containerDefinitions": [
    {
      "name": "prefect-server",
      "image": "<account-id>.<http://dkr.ecr.ap-southeast-1.amazonaws.com/prefect-server:latest|dkr.ecr.ap-southeast-1.amazonaws.com/prefect-server:latest>",
      "essential": true,
      "portMappings": [
        {
          "containerPort": 4200,
          "hostPort": 4200,
          "protocol": "tcp"
        }
      ],
      "environment": [
        {
          "name": "PREFECT_SERVER_API_HOST",
          "value": "0.0.0.0"
        },
        {
          "name": "PREFECT_SERVER_API_PORT",
          "value": "4200"
        },
        {
          "name": "PREFECT_UI_ENABLED",
          "value": "true"
        },
        {
          "name": "PREFECT_API_DATABASE_MIGRATE_ON_START",
          "value": "true"
        }
      ],
      "secrets": [
        {
          "name": "PREFECT_API_DATABASE_CONNECTION_URL",
          "valueFrom": "arn:aws:secretsmanager:ap-southeast-1:<account-id>:secret:prefect-db-url-abc123"
        }
      ],
      "logConfiguration": {
        "logDriver": "awslogs",
        "options": {
          "awslogs-group": "/ecs/prefect-server",
          "awslogs-region": "ap-southeast-1",
          "awslogs-stream-prefix": "ecs"
        }
      }
    }
  ]
}

What to put in PREFECT_API_DATABASE_CONNECTION_URL - Example value (store in Secrets Manager and reference via the Task Definition): -

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

- Make sure your ECS task’s security group can reach the RDS SG on port 5432. How your workers/CLI will reach the API - Set

PREFECT_API_URL

in worker/CLI environments to your reachable server URL: - Without a load balancer (host port mapping):

http://<ec2-instance-private-or-public-ip>:4200/api

- With an ALB / DNS:

<https://prefect>.<your-domain>/api

Useful docs - Prefect settings reference (all env vars): Settings reference - Self-hosted (Docker/Compose examples): Self-hosted with Docker/Compose Questions for you - Do you want the server to run inside ECS on that same EC2 host (above is set up for that), or do you prefer to run it as a plain Docker container (or Docker Compose/systemd) directly on the instance? I can provide a Compose file if that’s closer to your current setup.