How does reverse proxy works?

A reverse proxy works by intercepting client requests and forwarding them to one or more backend servers based on defined rules. It acts as a gateway between the client (usually a browser or other application) and the server that processes the request, hiding the identity of the actual server behind it.

Here’s a breakdown of how a reverse proxy works:

1. Client Request:

• When a user (client) tries to access a website, their browser sends a request (e.g., a request for a webpage) to the domain name (e.g., www.example.com).
• The DNS resolution process leads the client to the IP address of the reverse proxy rather than the actual web server.

2. Reverse Proxy Receives the Request:

• The reverse proxy receives the client’s request and checks its routing rules. It acts on behalf of the backend servers, so the client does not directly interact with the web server.
• The reverse proxy can perform several tasks at this point, such as:
  • Load balancing: Distributing the request to different backend servers based on their load or other criteria.
  • SSL Termination: If the request is encrypted (HTTPS), the reverse proxy can decrypt the data and then forward it to the backend server in plain HTTP.
  • Authentication and Authorization: The reverse proxy might check if the client has the necessary permissions to access the resources.
  • Caching: If the content requested by the client has been previously cached, the reverse proxy can serve the cached response directly to the client, which improves speed.

3. Forwarding Request to Backend Server:

• After processing (if necessary), the reverse proxy forwards the request to one of the backend servers that will handle it. The reverse proxy might choose the server using load balancing algorithms (like round-robin, least connections, or weighted distribution).

4. Backend Server Processes the Request:

• The backend server receives the request, processes it (e.g., fetches data from a database, generates dynamic content), and prepares a response.
• The backend server sends the response back to the reverse proxy.

5. Reverse Proxy Sends Response Back to Client:

• The reverse proxy receives the response from the backend server. Depending on the configuration, the reverse proxy might:
  • Cache the response for future use (if caching is enabled).
  • Modify the response: For example, it could add headers or compress the response to improve load times.
  • Secure the data: If the proxy handled SSL termination, it may re-encrypt the response before sending it to the client.
• Finally, the reverse proxy sends the response back to the client (e.g., a rendered webpage).

Key Functions & Benefits:

• Load Balancing: A reverse proxy can distribute incoming traffic across several backend servers to ensure no single server becomes overwhelmed.
• Security: By sitting between clients and servers, the reverse proxy can hide the internal infrastructure, protecting backend systems from direct access and potential attacks.
• Caching: Frequently requested content can be cached by the reverse proxy, reducing the need for repeated calls to the backend server and speeding up response times.
• SSL Termination: Offloading SSL encryption/decryption to the reverse proxy reduces the computational burden on backend servers, improving their efficiency.
• Simplified Architecture: It provides a single point of entry, simplifying network security and access management.

Example Flow:

1. Client: Requests https://www.test.com .
2. Reverse Proxy:
   • Receives the request.
   • Decides (e.g., based on load balancing rules) which backend server to forward the request to.
3. Backend Server: Processes the request and returns a response.
4. Reverse Proxy:
   • May cache the response or apply further processing.
   • Forwards the final response back to the client.

Example Technologies for Reverse Proxies:

• Nginx: A popular reverse proxy and web server, widely used for load balancing and caching.
• HAProxy: A high-performance reverse proxy for load balancing.
• Apache Traffic Server: An HTTP/1.1 and HTTP/2 compliant reverse proxy.
• Cloud-based services: CDNs like Cloudflare or AWS CloudFront act as reverse proxies for global content distribution.