Forward and Reverse Proxy in System Design

Proxies are one of the critical components in designing large-scale distributed systems. We use them to decouple clients from servers and provide additional functionalities like caching, authentication, logging, etc. So let's move forward and discuss two types of proxies: Forward proxy and Reverse proxy. One of the key goals here is to understand their differences.

What is Forward Proxy?

A forward proxy (also known as a proxy or proxy server) is a server that sits in front of a group of clients. When a client sends a request to a server, instead of going directly to the server, the request is routed to the forward proxy, which then forwards the request to the server.

In other words, when clients send requests to websites on the Internet, the forward proxy intercepts these requests and communicates with the servers on behalf of the clients (acting as an intermediary). This can help us to perform certain actions before the request reaches the original destination.

Why do we use a forward proxy?

There are several reasons to use a forward proxy.

• To filter network traffic based on predefined rules. For example, an organization can use a proxy server to block access to specific websites or restrict access to certain types of content. We can also use it to enforce security policies and protect against malicious activities.
• To provide anonymity for clients by hiding their IP addresses. This can be useful for accessing content that is restricted in certain regions or for protecting clients' privacy and security.
• To optimize network traffic by compressing data, removing unnecessary headers, and reducing the size of transferred data. This reduces bandwidth usage and improves network performance.

What is Reverse Proxy?

Reverse proxies are the exact opposite of forward proxies in terms of interaction pattern. A forward proxy acts on behalf of clients, and a reverse proxy acts on behalf of servers. So, unlike a forward proxy, which is used to protect clients, a reverse proxy is used to protect servers. To simplify the difference: A forward proxy ensures that no origin server ever communicates directly with that specific client. On the other hand, a reverse proxy ensures that no client ever communicates directly with that origin server.

When clients send requests to the server, the requests are intercepted by the reverse proxy. The reverse proxy will then send requests to and receive responses from the server. In other words, the client thinks it is directly interacting with the server, and the request goes to the reverse proxy without the client knowing about it (or does not know that some other server processed its request).

Let's take an example: Suppose we type "https://www.enjoyalgorithm.com" in our browser. Our browser makes a DNS query to get the IP address of enjoyalgorithm.com. If enjoyalgorithm.com uses a reverse proxy and configures it correctly, the DNS query will return the reverse proxy's IP address.

Use cases of reverse proxy

• By using a reverse proxy, we can hide the origin server's IP address from the clients so that malicious clients cannot access them directly. Reverse proxy can also implement features like rejecting traffic from specific client IP addresses (blacklisting) or limiting the number of requests accepted from each client.
• We can use a reverse proxy as a load-balancing solution to distribute traffic among servers.
• A reverse proxy can cache frequently requested resources like web pages, images, and videos. By serving cached content directly from the reverse proxy, we can reduce the load on the web server, speed up content delivery, save bandwidth, and decrease network latency.
• We can configure a reverse proxy to decrypt all incoming requests and encrypt all outgoing responses i.e. your origin server won't have to handle the encryption/decryption process for each client request. This can help to reduce the load on the origin server.

Disadvantages of reverse proxy

• Adding a reverse proxy to a system can increase its complexity.
• If the reverse proxy fails, the entire system can be affected, as all traffic goes through it. It is important to ensure redundancy and failover mechanisms to mitigate this risk.
• While a reverse proxy can improve performance by caching and load balancing, it can also introduce additional latency and overhead due to the additional processing required for each request.
• When SSL encryption is used, the reverse proxy must handle SSL certificates, which can be challenging to manage if there are many backend servers with different SSL configurations.

If you have any query or feedback, please write us at contact@enjoyalgorithms.com. Enjoy learning, Enjoy system design!