1. What is a Reverse Proxy?

A Reverse Proxy is a server that sits in front of one or more backend servers.

Clients never communicate with the backend servers directly.

Instead:

Client
   │
   ▼
Reverse Proxy
   │
   ▼
Backend Server

The client thinks it's talking to the application, but it's actually talking to the reverse proxy first.

The reverse proxy receives the request and forwards it to the appropriate backend server.

Without Reverse Proxy

Client

↓

Backend Server

Every client directly accesses your application.

With Reverse Proxy

          Client
             │
             ▼
      Reverse Proxy
             │
             ▼
      Backend Server

The backend server may not even be exposed to the internet.

2. Why Use a Reverse Proxy?

A reverse proxy does much more than simply forward requests.

A. Hide Backend Servers

Instead of exposing:

203.0.113.10
203.0.113.11
203.0.113.12

Clients only know:

api.example.com

The backend infrastructure remains hidden.

B. SSL/TLS Termination

Imagine HTTPS requests.

Without a reverse proxy:

Client

↓

HTTPS

↓

Every backend server

Every backend server needs:

• SSL certificates
• TLS handshake
• Encryption/decryption

Instead:

Client

↓

HTTPS

↓

Reverse Proxy

↓

HTTP

↓

Backend Server

The reverse proxy handles TLS once and forwards the request internally (often over a trusted private network).

This reduces complexity because backend servers don't all need to manage certificates.

Note: In higher-security environments, traffic between the reverse proxy and backend servers may also use HTTPS/TLS.

C. Load Balancing

A reverse proxy can distribute traffic.

            Reverse Proxy
           /      |      \
          ▼       ▼       ▼
      Server1 Server2 Server3

This is exactly what we learned in the previous topic.

D. Caching

Suppose 10,000 users request:

/logo.png

Without caching:

10,000 requests

↓

Backend Server

With a reverse proxy:

First request

↓

Backend

↓

Cache

Every later request:

Reverse Proxy

↓

Cached Response

The backend doesn't need to generate or fetch the same response repeatedly.

E. Compression

Large responses can be compressed before being sent.

Example:

500 KB JSON

↓

Compression

↓

100 KB

This reduces bandwidth and can improve response times.

F. Security

A reverse proxy can:

• Block malicious requests.
• Rate limit excessive traffic.
• Restrict access to certain endpoints.
• Hide internal server details.

3. What is Nginx?

Nginx (pronounced "Engine-X") is a high-performance web server that is also widely used as a:

• Reverse Proxy
• Load Balancer
• HTTP Cache
• Static File Server

One piece of software can perform several of these roles.

Example Architecture

             Internet
                 │
                 ▼
             Nginx
          /     |     \
         ▼      ▼      ▼
      Node1  Node2  Node3

Nginx receives every request.

It decides where to send it.

4. Why Backend Servers Use Reverse Proxies

Imagine a Node.js application.

Without Nginx:

Internet

↓

Node.js

Node.js now has to:

• Handle HTTPS
• Serve images
• Serve CSS
• Serve JavaScript
• Compress responses
• Cache files
• Load balance
• Handle application logic

That's a lot of responsibilities.

Instead:

Internet

↓

Nginx

↓

Node.js

Now the responsibilities are divided.

Nginx handles:

• HTTPS
• Static files
• Compression
• Caching
• Load balancing
• Reverse proxying

Node.js handles:

• Business logic
• Database operations
• Authentication
• APIs

Each component focuses on what it does best.

Reverse Proxy vs Load Balancer

Many people think they're the same, but they're not.

A reverse proxy can also act as a load balancer, which is why tools like Nginx are so popular.

Real-World Example

When you visit:

https://amazon.com

You are typically not connecting directly to an application server.

Instead, the request often follows a path like:

Browser

↓

Reverse Proxy / Load Balancer

↓

Application Servers

↓

Database

The browser only knows amazon.com; the internal server architecture is hidden behind the reverse proxy.

Interview Summary

• A Reverse Proxy sits between clients and backend servers, forwarding client requests to the appropriate backend.
• Clients communicate with the reverse proxy rather than directly with application servers.
• Reverse proxies can provide TLS termination, load balancing, caching, compression, security, and request routing.
• Nginx is a popular web server that is commonly used as a reverse proxy and load balancer.
• Using a reverse proxy lets backend applications (such as Node.js services) focus on business logic while infrastructure concerns are handled separately.

Connection with Previous Topics

Client
   │
 HTTPS
   │
   ▼
Nginx (Reverse Proxy)
   │
 HTTP/HTTPS
   │
   ▼
Load Balancing
   ├────────► Backend Server 1
   ├────────► Backend Server 2
   └────────► Backend Server 3

This ties together everything you've studied so far:

• HTTP/HTTPS → How communication happens.
• REST API → How APIs are designed.
• WebSocket → How real-time communication works.
• Load Balancer → How traffic is distributed.
• Reverse Proxy (Nginx) → The entry point that can terminate TLS, route requests, cache responses, and optionally load balance traffic before forwarding requests to backend services.