> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/donnemartin/system-design-primer/llms.txt
> Use this file to discover all available pages before exploring further.

# Reverse Proxy (Web Server)

> Understanding reverse proxies, their benefits, and comparison with load balancers

A reverse proxy is a web server that centralizes internal services and provides unified interfaces to the public. Requests from clients are forwarded to a server that can fulfill it before the reverse proxy returns the server's response to the client.

<img src="https://camo.githubusercontent.com/e88216b6d04c163f5e6e32f9e2e4d7fb84a2c4b0/687474703a2f2f692e696d6775722e636f6d2f6e3431417a66662e706e67" alt="Reverse Proxy" />

## Benefits

Additional benefits include:

* **Increased security** - Hide information about backend servers, blacklist IPs, limit number of connections per client
* **Increased scalability and flexibility** - Clients only see the reverse proxy's IP, allowing you to scale servers or change their configuration
* **SSL termination** - Decrypt incoming requests and encrypt server responses so backend servers do not have to perform these potentially expensive operations
  * Removes the need to install [X.509 certificates](https://en.wikipedia.org/wiki/X.509) on each server
* **Compression** - Compress server responses
* **Caching** - Return the response for cached requests
* **Static content** - Serve static content directly
  * HTML/CSS/JS
  * Photos
  * Videos
  * Etc

## Load Balancer vs Reverse Proxy

### When to Use Each

* **Load Balancer**: Deploying a load balancer is useful when you have multiple servers. Often, load balancers route traffic to a set of servers serving the same function.

* **Reverse Proxy**: Reverse proxies can be useful even with just one web server or application server, opening up the benefits described in the previous section.

* **Both**: Solutions such as NGINX and HAProxy can support both layer 7 reverse proxying and load balancing.

<Note>
  A reverse proxy can be beneficial even with a single backend server, while load balancers are specifically designed for distributing traffic across multiple servers.
</Note>

### Key Differences

| Aspect              | Load Balancer                              | Reverse Proxy                                              |
| ------------------- | ------------------------------------------ | ---------------------------------------------------------- |
| **Primary Purpose** | Distribute traffic across multiple servers | Centralize and manage access to backend services           |
| **Minimum Servers** | Multiple servers                           | Can work with single server                                |
| **Use Case**        | High availability and horizontal scaling   | Security, caching, SSL termination, serving static content |

<Accordion title="Disadvantages of Reverse Proxy">
  * Introducing a reverse proxy results in increased complexity.
  * A single reverse proxy is a single point of failure, configuring multiple reverse proxies (ie a [failover](https://en.wikipedia.org/wiki/Failover)) further increases complexity.
</Accordion>

## Source(s) and Further Reading

* [Reverse proxy vs load balancer](https://www.nginx.com/resources/glossary/reverse-proxy-vs-load-balancer/)
* [NGINX architecture](https://www.nginx.com/blog/inside-nginx-how-we-designed-for-performance-scale/)
* [HAProxy architecture guide](http://www.haproxy.org/download/1.2/doc/architecture.txt)
* [Wikipedia - Reverse proxy](https://en.wikipedia.org/wiki/Reverse_proxy)