Reverse Proxy

A primary function is to act as a traffic distributor, implementing algorithms like Round Robin, Least Connections, or Weighted Least Connections to spread client requests across a pool of backend servers. This prevents any single server from becoming a bottleneck, optimizing resource use, maximizing throughput, and ensuring high availability. In a fleet orchestration context, this is analogous to a central dispatcher assigning tasks to the most appropriate and available robot or vehicle based on current load and capability.

The reverse proxy handles the computationally expensive process of SSL/TLS termination. It decrypts incoming HTTPS traffic at the edge, inspects and routes the now-plaintext requests to backend servers, and re-encrypts responses for the client. This offloads cryptographic overhead from application servers, centralizes certificate management, and allows for inspection and manipulation of request content (e.g., header injection) that would be impossible with end-to-end encryption.

To reduce latency and backend load, reverse proxies can cache static and dynamic content. Frequently requested resources like images, CSS, JavaScript, and even API responses are stored locally on the proxy. Subsequent requests for the same content are served directly from the cache, dramatically improving response times for end-users and reducing the load on origin servers. This is a foundational principle of Content Delivery Networks (CDNs).

Positioned at the network edge, a reverse proxy acts as a security shield for backend infrastructure. Key security functions include:

• DDoS Protection: Absorbing and mitigating volumetric attacks.
• Web Application Firewall (WAF): Filtering out malicious HTTP traffic like SQL injection and cross-site scripting (XSS).
• IP Whitelisting/Blacklisting: Controlling access based on client IP.
• Request Rate Limiting: Preventing abuse and API exhaustion.
• Hiding Backend Topology: Internal server names, IPs, and architectures are concealed from external clients.

Reverse proxies optimize data transfer through on-the-fly compression (e.g., Gzip, Brotli) of server responses before sending them to the client, reducing bandwidth usage and improving page load times. They also perform protocol translation, allowing clients using modern protocols (like HTTP/2, HTTP/3) to communicate with backend servers that may only support HTTP/1.1, bridging compatibility gaps without requiring backend upgrades.

It provides a single public endpoint for multiple backend services, simplifying client configuration and DNS management. Using Layer 7 (application layer) routing rules, it can direct traffic based on the request's hostname, URL path, headers, or cookies. For example, requests to api.example.com go to the API cluster, while requests to app.example.com/images/* go to a dedicated image server. This enables clean microservices architectures and name-based virtual hosting.

A Load Balancer is a device or software that distributes network traffic across multiple backend servers. A reverse proxy is a type of Layer 7 (application) load balancer.

• Layer 4 vs. Layer 7: Network Load Balancers (L4) route based on IP and TCP/UDP port. Application Load Balancers (L7, like a reverse proxy) route based on HTTP headers, URLs, or cookies.
• Core Algorithms: Implements logic like Round Robin, Least Connections, or IP Hash to distribute requests efficiently and ensure high availability.
• Integrated Role: For modern web traffic, the reverse proxy and application load balancer are often the same component, providing both routing and value-added services like caching.