If you work with web applications, you’ve heard these terms: CDN, Load Balancer, Reverse Proxy, and API Gateway. People often mix them up or think they do the same thing. They don’t.

Each component solves a different problem. Understanding when and where to use each one will save you time and prevent headaches.

Contents

What Each Component Actually Does

Load Balancer

A load balancer takes incoming requests and spreads them across multiple servers. Think of it like a traffic cop directing cars to different lanes to prevent jams.

When you visit Amazon, millions of other people are doing the same thing. Without load balancers, one server would crash from too much traffic while others sit empty.

Example: You have 3 web servers. The load balancer sends every 3rd request to a different server. If one server dies, it stops sending traffic there.

Reverse Proxy

A reverse proxy sits between users and your servers. It handles requests on behalf of your servers. Users think they’re talking directly to your server, but they’re actually talking to the proxy.

Example: When you visit a website with HTTPS, the reverse proxy handles the encryption. It decrypts the request, forwards it to your server, gets the response, encrypts it, and sends it back to you.

API Gateway

An API gateway manages API calls. It’s like a bouncer at a club - it checks if you’re allowed in, what you can access, and how often you can make requests.

Example: A mobile app makes 100 API calls per minute. The API gateway checks the app’s API key, allows 90 calls, and blocks 10 because they hit the rate limit.

CDN (Content Delivery Network)

A CDN stores copies of your content in servers around the world. When someone requests your content, they get it from the server closest to them.

Example: Your website serves a 5MB video. Without CDN, users in Japan download it from your server in Virginia. With CDN, they download it from a server in Tokyo. Much faster.

How They Differ

Component Main Job Where It Lives What It Caches
Load Balancer Spread traffic across servers Your data center Nothing
Reverse Proxy Handle requests for servers Your data center Web pages, images
API Gateway Manage API access Your data center API responses
CDN Deliver content globally Edge locations worldwide Static files, media

The Wrong Way to Think About Order

Most people think there’s a “correct” order to place these components:

Internet → CDN → API Gateway → Reverse Proxy → Load Balancer → Servers

This is wrong. The order depends on what problem you’re trying to solve.

Different Orders for Different Goals

Goal: Stop Attacks Early

Internet → Reverse Proxy → Load Balancer → CDN → API Gateway → Servers

Put the reverse proxy first to block bad requests before they reach anything else. Banks and hospitals do this.

Goal: Fast Global Access

Internet → CDN → Load Balancer → Reverse Proxy → API Gateway → Servers

Put CDN first so users get content from nearby servers. Netflix and YouTube do this.

Goal: Control API Access

Internet → API Gateway → CDN → Reverse Proxy → Load Balancer → Servers

Put API gateway first to validate API keys before serving any content. SaaS companies do this.

Goal: Handle Multiple Regions

Internet → Load Balancer → CDN → Reverse Proxy → API Gateway → Servers

Put load balancer first to route traffic to the right region based on where users are located.

Real Examples

E-commerce Site (Like Amazon)

Customer → CDN (product images) → API Gateway (shopping cart API) → Reverse Proxy (SSL) → Load Balancer → Web servers

The CDN serves product images fast. The API gateway manages shopping cart requests. The reverse proxy handles HTTPS. The load balancer spreads traffic across web servers.

Social Media (Like Instagram)

User → API Gateway (mobile app requests) → CDN (photos/videos) → Reverse Proxy (web features) → Load Balancer → App servers

Mobile apps hit the API gateway first for authentication. Photos and videos come from CDN. Web features go through reverse proxy. Load balancer distributes to app servers.

Banking App

Customer → Reverse Proxy (security checks) → Load Balancer (regional routing) → CDN (documents) → API Gateway (transactions) → Servers

Security checks happen first. Regional routing for compliance. Documents cached in CDN. Transaction APIs go through gateway.

Common Mistakes

Mistake 1: Using Everything Everywhere

You don’t need all four components for every application. A simple blog might only need a CDN. A complex API might need all four.

Mistake 2: Same Order for Everything

Different parts of your application might need different orders. Static files go CDN-first. API calls might go API Gateway-first.

Mistake 3: Ignoring Geography

If your users are global, CDN placement matters. If your users are local, focus on load balancer and reverse proxy.

Mistake 4: Security as an Afterthought

If security is critical, put reverse proxy early in the chain. Don’t add security last.

Decision Framework

Ask yourself these questions:

  1. Where are my users? Global = CDN important. Local = load balancer important.
  2. What’s my biggest risk? Security = reverse proxy first. Performance = CDN first.
  3. How complex are my APIs? Simple = basic load balancer. Complex = API gateway.
  4. What breaks if it’s slow? Critical paths need optimization.

Monitoring All Components

Each component needs monitoring:

  • Load Balancer: Server health, response times
  • Reverse Proxy: SSL certificate expiry, cache hit rates
  • API Gateway: API response times, rate limit hits
  • CDN: Cache hit rates, origin server load

Start Simple

Begin with one component that solves your biggest problem:

  • Slow global users? Add CDN.
  • Servers crashing? Add load balancer.
  • API security issues? Add API gateway.
  • SSL management headaches? Add reverse proxy.

Add other components as you grow and face new problems.

Summary

These four components solve different problems:

  • Load Balancer: Distributes traffic
  • Reverse Proxy: Handles requests
  • API Gateway: Manages APIs
  • CDN: Delivers content globally

The order you use them depends on your goals, not some universal rule. Start with your biggest problem and add components as needed.

Security-first organizations put reverse proxy early. Performance-first organizations put CDN early. API-first organizations put API gateway early.

Choose the order that matches your priorities, not what someone else is doing.

Feel free to contact me for any suggestions and feedbacks. I would really appreciate those.

Thank you for reading!

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