How to Deploy FastAPI to AWS: Step-by-Step Guide

To deploy FastAPI to AWS, you can use AWS Elastic Beanstalk for easy server management or AWS Lambda with API Gateway for serverless deployment. Package your FastAPI app with a Dockerfile or use Uvicorn as the ASGI server, then upload and configure it on AWS.

Syntax

Deploying FastAPI to AWS typically involves these parts:

• FastAPI app: Your Python code defining API endpoints.
• ASGI server: Usually uvicorn to run the app.
• Dockerfile (optional): Defines how to containerize your app for AWS Elastic Beanstalk or ECS.
• AWS service: Choose between Elastic Beanstalk (managed servers) or Lambda (serverless).
• Deployment commands: AWS CLI or AWS Console to upload and start your app.

dockerfile

FROM python:3.10-slim
WORKDIR /app
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt
COPY . .
CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]

Example

This example shows a simple FastAPI app and how to deploy it on AWS Elastic Beanstalk using Docker.

python

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def read_root():
    return {"message": "Hello from FastAPI on AWS!"}

# Dockerfile
# ----------------
# FROM python:3.10-slim
# WORKDIR /app
# COPY requirements.txt .
# RUN pip install --no-cache-dir -r requirements.txt
# COPY . .
# CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]

# Deployment steps:
# 1. eb init -p docker fastapi-app
# 2. eb create fastapi-env
# 3. eb open

Output

{"message": "Hello from FastAPI on AWS!"}

Common Pitfalls

Common mistakes when deploying FastAPI to AWS include:

• Not exposing the correct port (AWS expects 8080 or 8000).
• Forgetting to include uvicorn in the Docker CMD or startup command.
• Not setting host='0.0.0.0' in uvicorn, which makes the app unreachable externally.
• Missing AWS Elastic Beanstalk configuration files like Dockerrun.aws.json if not using Dockerfile.
• Ignoring AWS Lambda timeout limits if using serverless deployment.

Wrong example:

CMD ["uvicorn", "main:app"]  # Missing host and port

Right example:

CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]

Quick Reference

Summary tips for deploying FastAPI to AWS:

• Use uvicorn with --host 0.0.0.0 and proper port.
• Choose Elastic Beanstalk for easy server management or Lambda for serverless.
• Containerize with Docker for consistent environments.
• Use AWS CLI commands like eb init and eb create for Elastic Beanstalk deployment.
• Test locally with Docker before deploying.

Key Takeaways

Use Docker and Uvicorn with host 0.0.0.0 to make FastAPI accessible on AWS.

Elastic Beanstalk is a simple way to deploy FastAPI with managed servers.

AWS Lambda with API Gateway offers serverless deployment but watch timeout limits.

Always test your container locally before deploying to AWS.

Configure AWS CLI and Elastic Beanstalk properly for smooth deployment.