Does FastAPI Work With AWS?
FastAPI works excellently with AWS—deploy it on Lambda, EC2, ECS, or App Runner and integrate with AWS services for a production-ready serverless or containerized backend.
Quick Facts
How FastAPI Works With AWS
FastAPI integrates seamlessly with AWS through multiple deployment paths. The most popular approach is AWS Lambda using Mangum (ASGI adapter) to wrap the FastAPI application, enabling serverless execution with API Gateway as the HTTP trigger. For container-based deployments, FastAPI runs on ECS, App Runner, or EC2 with standard Docker containerization. AWS SDK (boto3) integrates naturally for accessing S3, DynamoDB, SQS, and other services. The developer experience is smooth—write FastAPI code normally, then deploy via CDK, CloudFormation, or the AWS console. Architecture considerations include cold start latency for Lambda (mitigated by provisioned concurrency), setting appropriate IAM roles for boto3 calls, and managing environment variables for API keys. FastAPI's automatic OpenAPI documentation works great for documenting AWS-backed APIs, and request/response validation happens before hitting AWS services, reducing unnecessary calls.
Best Use Cases
FastAPI on AWS Lambda with Mangum
pip install fastapi mangum boto3from fastapi import FastAPI
from mangum import Mangum
import boto3
app = FastAPI()
s3_client = boto3.client('s3')
@app.get("/")
async def read_root():
return {"message": "Hello from AWS Lambda"}
@app.get("/buckets")
async def list_s3_buckets():
response = s3_client.list_buckets()
return {"buckets": [b['Name'] for b in response['Buckets']]}
@app.post("/upload")
async def upload_file(bucket: str, key: str, data: str):
s3_client.put_object(Bucket=bucket, Key=key, Body=data)
return {"status": "uploaded", "bucket": bucket, "key": key}
# Handler for AWS Lambda
handler = Mangum(app)Known Issues & Gotchas
Lambda cold starts cause 1-5 second delays on first invocation; users experience slow initial requests
Fix: Use Lambda Provisioned Concurrency or switch to App Runner/ECS for consistently warm instances. Alternative: implement caching and async patterns.
Mangum doesn't support WebSocket properly in Lambda (API Gateway v1); real-time features break
Fix: Use WebSocket-compatible deployment (ECS, App Runner) or API Gateway v2 with proper Mangum configuration for asyncio.
IAM permission errors silently fail during boto3 calls if roles aren't configured correctly
Fix: Attach proper IAM policies to Lambda execution role; test with AWS CloudTrail logs to debug permission denials.
FastAPI debug=True leaks sensitive information in production; AWS Lambda environments expose stack traces publicly
Fix: Always set debug=False in production; use environment variables to toggle settings based on deployment stage.
Alternatives
- •Flask + Zappa on AWS Lambda (older, less features than FastAPI)
- •Node.js Express with AWS Amplify (better for TypeScript; similar serverless workflow)
- •Django on AWS Elastic Beanstalk (heavier, more batteries-included, better for monoliths)
Resources
Related Compatibility Guides
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