Introduction

AWS Lambda allows developers to run applications without managing servers, making it an excellent choice for serverless Flask applications. By integrating AWS API Gateway, we can deploy Flask-based APIs in a fully managed, scalable environment.

This guide covers:
✅ Setting up Flask for AWS Lambda
✅ Configuring API Gateway
✅ Deploying with Zappa
✅ Optimizing and troubleshooting

Why Use AWS Lambda for Flask?

  • Scalability: AWS handles automatic scaling
  • Cost-efficient: Pay only for the execution time
  • Managed infrastructure: No need to maintain servers
  • High availability: Redundant and distributed

Step 1: Setting Up Flask

First, install Flask and create a simple application.

pip install flask

Creating a Flask App

from flask import Flask, jsonify

app = Flask(__name__)

@app.route("/")
def home():
return jsonify({"message": "Flask on AWS Lambda!"})

if __name__ == "__main__":
app.run(debug=True)

Step 2: Installing Zappa for AWS Deployment

Zappa is a Python package that simplifies Flask deployment to AWS Lambda.

Install Zappa

pip install zappa

Initialize Zappa

Inside your project folder, run:

zappa init

This will prompt for:

  • S3 bucket for Lambda packaging
  • AWS region (choose the closest one)
  • Project name

Step 3: Deploying Flask on AWS Lambda

Once initialized, deploy the app using:

zappa deploy

After deployment, Zappa will return a URL, e.g.,:

https://abcd1234.execute-api.us-east-1.amazonaws.com/dev

Your Flask API is now live on AWS Lambda! 🎉

Step 4: Configuring API Gateway

AWS API Gateway is used to route requests to the Lambda function.

Updating API Gateway Settings

  • Go to AWS Console > API Gateway
  • Select the deployed API
  • Under CORS settings, enable OPTIONS method
  • Deploy API changes

Step 5: Custom Domain & HTTPS

To use a custom domain:

zappa certify

This configures an SSL certificate for HTTPS.

Step 6: Optimizing Performance

  1. Reduce Cold Start: Use provisioned concurrency
  2. Optimize Response Time: Enable API Gateway caching
  3. Reduce Deployment Size: Use requirements.txt

Step 7: Updating & Rolling Back

To update your function:

zappa update

To rollback to a previous version:

zappa rollback

Conclusion

Deploying Flask on AWS Lambda with Zappa offers scalability, cost savings, and serverless advantages. With API Gateway integration, you can run Flask APIs without managing servers.

🚀 Start building your serverless Flask API today!