🗓️ 07112025 1440

REVERSE PROXY

Core Concept:

  • Server between clients and backend servers
  • Forwards client requests to appropriate backends
  • Returns backend responses to clients
  • Hides backend topology from clients

Why It Matters​

  • Abstraction layer that hides backend server topology from clients
  • Single entry point for multiple backend services
  • Offloads work from application servers (SSL termination, caching, compression)

When to Use​

  • Need to load balance across multiple backend servers
  • Want to cache responses to reduce backend load
  • Need SSL termination to offload encryption work from app servers
  • Want single public IP for multiple internal services
  • Need to compress responses before sending to clients
  • Want to add security layer (WAF, DDoS protection)

When Not to Use​

  • Single backend server with low traffic (adds unnecessary complexity)
  • Need direct client-to-server communication for real-time protocols
  • Latency-critical applications where extra hop is unacceptable

Trade-offs​

Benefits:

  • Improved security (hides backend topology)
  • Better performance (caching, compression)
  • Simplified SSL management (terminate at proxy)
  • Flexible routing and load balancing
  • Centralized monitoring and logging

Drawbacks:

  • Additional latency (extra network hop)
  • Single point of failure (needs HA setup)
  • Increased infrastructure complexity
  • Resource overhead for proxy operations

Key Distinctions​

Reverse Proxy vs Forward Proxy:

  • Reverse Proxy: Works on behalf of servers, clients unaware of backend topology
  • Forward Proxy: Works on behalf of clients, servers unaware of original client
  • Reverse proxy sits in front of servers; forward proxy sits in front of clients

Reverse Proxy vs Load Balancer:

  • Load Balancer: Focused on distributing traffic across multiple servers
  • Reverse Proxy: Broader functionality (caching, SSL, compression, routing)
  • Load balancer is a specific use case of reverse proxy
  • Many reverse proxies include load balancing features

This relates to load_balancer for traffic distribution and api_gateway which adds API-specific features on top of reverse proxy capabilities.

Common Pitfalls​

WARNING

Connection pooling misconfiguration: Not reusing backend connections leads to connection exhaustion. Configure keep-alive properly.

DANGER

Health check failures: If reverse proxy doesn't detect unhealthy backends, it will route requests to failed servers. Always configure health checks.

Quick Reference​

SolutionStrengthsUse Case
NGINXHigh performance, low memoryStatic content, load balancing
HAProxyAdvanced load balancingTCP/HTTP load balancing
ApacheFeature-rich, flexibleTraditional web hosting
TraefikDynamic config, Docker-nativeMicroservices, containers
EnvoyModern, service mesh readyCloud-native, gRPC

Key Features​

  • Load Balancing: Distribute requests across backend servers
  • SSL Termination: Decrypt HTTPS at proxy, use HTTP to backends
  • Caching: Store responses to reduce backend load
  • Compression: Gzip/Brotli responses before sending
  • Request Routing: Route based on URL path, headers, host
  • Header Manipulation: Add/remove/modify headers
  • Rate Limiting: Control request frequency per client
  • Health Checks: Monitor backend server availability

Basic NGINX Configuration Example​

upstream backend {
    server backend1.example.com:8080;
    server backend2.example.com:8080;
    server backend3.example.com:8080;
}

server {
    listen 80;
    server_name example.com;

    location / {
        proxy_pass http://backend;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        
        # Caching
        proxy_cache my_cache;
        proxy_cache_valid 200 60m;
        
        # Timeouts
        proxy_connect_timeout 60s;
        proxy_send_timeout 60s;
        proxy_read_timeout 60s;
    }
}

References​