Deploy FastAPI on AWS Lambda in just 9 minutes

FastAPI is a modern, fast (high-performance), web framework for building APIs with Python 3.6+ based on standard Python type hints. It is built on top of Starlette for the web parts, and Pydantic for the data parts. FastAPI is known for its speed, simplicity, and ease of use in creating APIs.

AWS Lambda is a serverless computing service provided by Amazon Web Services. Using AWS Lambda, you can run your code without provisioning or managing servers. AWS Lambda automatically scales your application by running code in response to each trigger, which helps you to build highly scalable applications.

In this tutorial, we will learn how to deploy a FastAPI application on AWS Lambda in just 9 minutes. Let’s get started!

Prerequisites:

1. A basic understanding of Python and FastAPI.
2. An AWS account with the necessary permissions to create AWS Lambda functions.

Step 1: Install required libraries
First, let’s install the required libraries for our FastAPI application:

pip install fastapi uvicorn

Step 2: Create a FastAPI application
Next, let’s create a simple FastAPI application. Create a file named main.py and add the following code:

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def read_root():
    return {"Hello": "World"}

This code creates a simple FastAPI application with a single endpoint that returns a JSON response.

Step 3: Test the FastAPI application locally
Before deploying our FastAPI application on AWS Lambda, let’s test the application locally. Run the following command to start the FastAPI application using Uvicorn:

uvicorn main:app --reload

Visit http://127.0.0.1:8000 in your browser and you should see the JSON response {"Hello": "World"}.

Step 4: Package the FastAPI application for AWS Lambda
To deploy our FastAPI application on AWS Lambda, we need to package it along with all its dependencies into a ZIP file. To do this, create a file named lambda_function.py and add the following code:

import os
from aws_lambda_powertools.logging import LoggerFactory
from aws_lambda_powertools.tracing import Tracer

tracer = Tracer()
logger = LoggerFactory().get_logger()

os.environ["FASTERAPI_ENV"] = "AWS_LAMBDA"
from fastapi_lambda import FastAPILambda
from main import app

fastapi_lambda = FastAPILambda(app)

Next, install the required library for AWS Lambda:

pip install aws-lambda-powertools aws-lambda-fastapi

Now, create a ZIP file containing the main.py, lambda_function.py, and the site-packages directory with the required dependencies. You can achieve this by running the following command:

zip -r9 lambda.zip main.py lambda_function.py site-packages

Step 5: Create an AWS Lambda function
Now, let’s create an AWS Lambda function for our FastAPI application. Follow these steps:

1. Sign in to the AWS Management Console and open the Lambda console.
2. Click on the Create function button.
3. Choose Author from scratch and give your Lambda function a name and select the Python 3.8 runtime.
4. Upload the lambda.zip file that we created in the previous step.
5. Set the handler to lambda_function.fastapi_lambda.handler.
6. Create or choose an existing execution role with sufficient permissions.
7. Click on Create function to create the Lambda function.

Step 6: Configure API Gateway
To create a public endpoint for our FastAPI application, we need to configure API Gateway. Follow these steps:

1. Click on Add trigger in the Lambda function.
2. Choose API Gateway as the trigger type.
3. In the Create a new API dropdown, choose HTTP API.
4. Click on Add to create the API Gateway trigger.

Step 7: Deploy the API Gateway
To make the API Gateway accessible publicly, we need to deploy the API. Follow these steps:

1. Go to the API Gateway service in the AWS Management Console.
2. Select the API that is connected to your Lambda function.
3. Click on Actions and choose Deploy API.
4. Select the deployment stage (e.g., prod) and click on Deploy.

Step 8: Test the deployed FastAPI on AWS Lambda
Now that our FastAPI application is deployed on AWS Lambda, we can test it by hitting the public endpoint provided by API Gateway. Copy the URL of the deployed API and paste it into your browser. You should see the JSON response {"Hello": "World"}.

Congratulations! You have successfully deployed a FastAPI application on AWS Lambda. You can now expand your application, add more endpoints, and integrate it with other AWS services.

I hope this tutorial was helpful in guiding you through the process of deploying FastAPI on AWS Lambda in just 9 minutes. Thank you for reading!