Creating custom middleware in Django - Performance Optimization Steps

Performance: Creating custom middleware

MEDIUM IMPACT

This affects the request-response cycle speed and server processing time, impacting how fast pages start loading.

Adding custom logic to process requests and responses

Django

class FastMiddleware:
    def __init__(self, get_response):
        self.get_response = get_response

    def __call__(self, request):
        # Minimal processing, no blocking calls
        response = self.get_response(request)
        return response

Avoids blocking calls and heavy processing, keeping request handling fast.

📈 Performance GainReduces blocking time to near 0ms, improving LCP

Adding custom logic to process requests and responses

Django

class SlowMiddleware:
    def __init__(self, get_response):
        self.get_response = get_response

    def __call__(self, request):
        import time
        time.sleep(1)  # Simulate slow processing
        response = self.get_response(request)
        return response

This middleware blocks the request for 1 second, delaying every page load.

📉 Performance CostBlocks rendering for 1000ms per request, increasing LCP significantly

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Heavy blocking middleware	0 (server-side)	0 (client-side)	0 (client-side)	[X] Bad
Lightweight middleware	0 (server-side)	0 (client-side)	0 (client-side)	[OK] Good

Rendering Pipeline

Middleware runs on the server before the response is sent to the browser, affecting how quickly the browser can start rendering.

→Server Processing

→Network Transfer

→Browser Rendering

⚠️ BottleneckServer Processing time caused by middleware logic

Core Web Vital Affected

LCP

This affects the request-response cycle speed and server processing time, impacting how fast pages start loading.

Optimization Tips

1Avoid blocking calls inside middleware to keep server response fast.

2Keep middleware logic simple and efficient to reduce delay.

3Use DevTools Network tab to monitor server response times.

Performance Quiz - 3 Questions

How does heavy processing in custom middleware affect page load?

A It improves network speed

B It increases server response time, delaying page load

C It reduces browser paint time

D It decreases DOM size

DevTools: Network

How to check: Open DevTools, go to Network tab, reload page, and check the Time column for server response delays.

What to look for: Look for long 'Waiting (TTFB)' times indicating slow server processing possibly caused by middleware.