Fullstack Python: Containerizing Flask Apps and Deploying on AWS ECS

August 01, 2025

In modern fullstack development, containerization has become a standard practice for deploying scalable, consistent, and portable applications. When combined with Amazon ECS (Elastic Container Service), developers can efficiently run and manage Dockerized Flask apps in the cloud. In this blog, we'll walk through how to containerize a Flask application and deploy it on AWS ECS.

Why Containerize Your Flask App?

Containers package your application with all its dependencies, ensuring it runs consistently across development, staging, and production. Benefits include:

Portability across environments

Faster deployments

Easier scaling

Better resource utilization

Compatibility with orchestration tools like Kubernetes and AWS ECS

Step 1: Create and Containerize the Flask App

Assume you have a basic Flask app in a file called app.py.

app.py

python

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from flask import Flask

app = Flask(__name__)

@app.route('/')

def home():

return "Hello from Flask in ECS!"

requirements.txt

nginx

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flask

gunicorn

Now, create a Dockerfile:

dockerfile

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# Dockerfile

FROM python:3.9-slim

WORKDIR /app

COPY requirements.txt .

RUN pip install --no-cache-dir -r requirements.txt

COPY . .

CMD ["gunicorn", "-b", "0.0.0.0:5000", "app:app"]

Build and test your container locally:

bash

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docker build -t flask-ecs-app .

docker run -p 5000:5000 flask-ecs-app

Step 2: Push Docker Image to Amazon ECR

Amazon ECR (Elastic Container Registry) is where your Docker image will live before ECS uses it.

Create an ECR repository:

bash

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aws ecr create-repository --repository-name flask-ecs-app

Authenticate Docker to your ECR registry:

bash

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aws ecr get-login-password | docker login --username AWS --password-stdin <aws_account_id>.dkr.ecr.<region>.amazonaws.com

Tag and push your image:

bash

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docker tag flask-ecs-app <your-repo-url>:latest

docker push <your-repo-url>:latest

Step 3: Set Up ECS Cluster and Service

Go to the AWS Management Console, and do the following:

Create a Cluster:

Choose “EC2” or “Fargate” depending on your use case.

Fargate is serverless and easier to manage for beginners.

Create a Task Definition:

Use the image you pushed to ECR.

Set container memory and CPU (e.g., 512 MB and 0.25 vCPU).

Map port 5000 for the container.

Create a Service:

Link it to your cluster.

Choose the number of desired tasks (instances of your app).

Configure load balancer (optional but recommended for production).

Step 4: Access Your Deployed Flask App

If using a load balancer, access the app using its DNS name. If not, use the public IP of the ECS-hosted instance or Fargate task.

Conclusion

Deploying a Flask app on AWS ECS after containerization offers reliability, scalability, and flexibility for fullstack developers. With Docker, your app is portable and easy to manage, and ECS simplifies orchestration without needing to manage infrastructure manually. As your app scales, ECS can handle increased traffic, rolling updates, and auto-healing, making it an ideal platform for production-ready deployments.

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