Throttling for rate limiting in Django - Performance & Optimization

Performance: Throttling for rate limiting

MEDIUM IMPACT

Throttling controls how often users can send requests, impacting server response time and page load speed under heavy traffic.

Limiting user requests to prevent server overload

Django

from rest_framework.throttling import UserRateThrottle

class CustomRateThrottle(UserRateThrottle):
    rate = '10/minute'

# In settings.py
REST_FRAMEWORK = {
    'DEFAULT_THROTTLE_CLASSES': ['path.to.CustomRateThrottle'],
    'DEFAULT_THROTTLE_RATES': {'user': '10/minute'},
}

# Uses cache backend for counting with expiration and async support

Uses Django REST Framework's built-in throttling with cache backend, which efficiently tracks requests with expiration and avoids blocking, improving response times.

📈 Performance GainNon-blocking request handling; cache limits memory use; reduces server load spikes

Limiting user requests to prevent server overload

Django

from django.utils.decorators import decorator_from_middleware

class SimpleThrottleMiddleware:
    def __init__(self, get_response):
        self.get_response = get_response
        self.requests = {}

    def __call__(self, request):
        user_ip = request.META.get('REMOTE_ADDR')
        count = self.requests.get(user_ip, 0)
        if count >= 10:
            from django.http import HttpResponseTooManyRequests
            return HttpResponseTooManyRequests('Too many requests')
        self.requests[user_ip] = count + 1
        return self.get_response(request)

# Middleware stores counts in memory without expiration or persistence

This approach stores request counts in memory without expiration, causing memory growth and inaccurate throttling after server restarts. It also blocks requests synchronously, increasing response time under load.

📉 Performance CostBlocks rendering for extra milliseconds per request under load; memory usage grows unbounded

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
In-memory synchronous throttling	N/A	N/A	Increases server response delay	[X] Bad
Cache-backed async throttling (DRF)	N/A	N/A	Minimal server delay, faster response	[OK] Good

Rendering Pipeline

Throttling checks happen before view processing, affecting server response time and thus the time until the browser receives content to render.

→Server Request Handling

→Response Generation

⚠️ BottleneckServer Request Handling when throttling is inefficient or blocking

Core Web Vital Affected

INP

Throttling controls how often users can send requests, impacting server response time and page load speed under heavy traffic.

Optimization Tips

1Use cache-backed throttling to limit memory growth and improve response times.

2Avoid synchronous blocking in throttling logic to keep server responsive.

3Set reasonable rate limits to balance user experience and server load.

Performance Quiz - 3 Questions

What is the main performance benefit of using cache-backed throttling in Django?

A It increases the number of allowed requests per second.

B It reduces server memory usage and avoids blocking requests.

C It eliminates the need for any request validation.

D It speeds up client-side rendering directly.

DevTools: Network

How to check: Open DevTools, go to Network tab, filter requests and observe response times and status codes when sending many requests quickly.

What to look for: Look for HTTP 429 status codes indicating throttling and check if response times stay low under load.