Rate Limiting and Throttling in Django and FastAPI

Introduction

In modern APIs, preventing abuse, mitigating brute-force attacks, and managing resource usage is critical. That’s where rate limiting and request throttling come in. Both Django and FastAPI provide mechanisms to control traffic and protect your backend from being overwhelmed.

🔒 Related: JWT Authentication in Django and FastAPI

Why Rate Limiting Matters

• Security: Prevent brute-force login attacks
• Stability: Avoid excessive resource consumption
• Fair Usage: Enforce API usage policies

Let’s explore how to set up and customize rate limiting in Django and FastAPI.

Django: Using Django REST Framework Throttling

Django REST Framework (DRF) offers built-in throttling classes:

Step 1: Enable Throttling in settings.py

REST_FRAMEWORK = {
    'DEFAULT_THROTTLE_CLASSES': [
        'rest_framework.throttling.UserRateThrottle',
        'rest_framework.throttling.AnonRateThrottle',
    ],
    'DEFAULT_THROTTLE_RATES': {
        'user': '1000/day',
        'anon': '100/day',
    }
}

Step 2: Customize if Needed

You can define custom throttling classes by subclassing BaseThrottle or SimpleRateThrottle.

FastAPI: Using SlowAPI or Middleware

FastAPI doesn’t come with built-in throttling, but the SlowAPI library integrates seamlessly.

Step 1: Install SlowAPI

pip install slowapi

Step 2: Integrate SlowAPI

from fastapi import FastAPI, Request
from slowapi import Limiter
from slowapi.util import get_remote_address
from slowapi.errors import RateLimitExceeded
from fastapi.responses import JSONResponse

limiter = Limiter(key_func=get_remote_address)
app = FastAPI()
app.state.limiter = limiter

@app.exception_handler(RateLimitExceeded)
async def rate_limit_handler(request: Request, exc: RateLimitExceeded):
    return JSONResponse(
        status_code=429,
        content={"detail": "Rate limit exceeded"}
    )

@app.get("/ping")
@limiter.limit("5/minute")
async def ping():
    return {"message": "pong"}

Fine-Tuning and Advanced Usage

• User-specific limits: Use tokens or headers to rate-limit per user
• Dynamic limits: Change limits based on subscription level
• Redis backend: Both DRF and SlowAPI can use Redis to manage state efficiently

Gotchas and Best Practices

• Always handle 429 Too Many Requests gracefully
• Monitor usage and adjust limits proactively
• Document rate limits in your API docs (e.g. OpenAPI spec)

Cross-Framework Tip

• Django’s DRF is great for plug-and-play throttling.
• FastAPI gives more flexibility but requires third-party tools.
• For background operations, pair this with Background Tasks in FastAPI to handle overflow without blocking the user.

🧠 Related: Preventing N+1 Query Problems in Django and FastAPI

Conclusion

Rate limiting is essential for a secure and performant API. Whether you’re building with Django or FastAPI, both frameworks offer practical ways to prevent abuse and ensure fair access.

⚙️ If you’re scaling your app, don’t forget to check out Database Connection Pooling in FastAPI with SQLAlchemy

📌 Up next: Testing APIs in Django and FastAPI: Best Practices and Tools