While both technologies route client requests to backend servers, their architectural purposes differ fundamentally:

// Reverse Proxy Example (Nginx)
server {
    listen 80;
    server_name example.com;
    
    location / {
        proxy_pass http://backend_server;
        proxy_set_header Host $host;
        proxy_cache_bypass $http_upgrade;
    }
}

// Load Balancer Example (HAProxy)
frontend http-in
    bind *:80
    default_backend servers

backend servers
    balance roundrobin
    server server1 192.168.1.1:80 check
    server server2 192.168.1.2:80 check

Reverse proxies typically operate at Layer 7 (application layer):

• HTTP/HTTPS header manipulation
• SSL termination
• Content caching

Load balancers often work at Layer 4 (transport layer):

• TCP/UDP connection forwarding
• Basic packet inspection
• No application-layer awareness

Reverse proxies offer sophisticated request processing:

# Apache mod_proxy rules
ProxyPass /api/v1 http://api-v1-cluster
ProxyPass /api/v2 http://api-v2-cluster
ProxyPassReverse /api/v1 http://api-v1-cluster

Load balancers focus on distribution algorithms:

# AWS ALB Target Group configuration
"TargetGroups": [
    {
        "HealthCheckPath": "/status",
        "Algorithm": "least_outstanding_requests"
    }
]

Throughput benchmarks show significant differences:

Modern architectures often combine both:

// Cloudflare Worker implementing both
addEventListener('fetch', event => {
    const url = new URL(event.request.url)
    
    // Reverse proxy logic
    if(url.pathname.startsWith('/static')) {
        return event.respondWith(cacheFirst(event.request))
    }
    
    // Load balancing logic
    const backend = BACKENDS[Math.floor(Math.random()*BACKENDS.length)]
    return event.respondWith(fetch(backend + url.pathname))
})

While both load balancers and reverse proxies handle request distribution, they serve fundamentally different purposes in system architecture.

Load Balancer: Primarily focuses on distributing client requests across multiple servers to optimize resource utilization and ensure high availability.

Reverse Proxy: Acts as an intermediary for requests from clients seeking resources from servers, providing additional functionality like caching, SSL termination, and security.

Here's a simple Nginx configuration showing both concepts:

# Load Balancer Configuration
upstream backend {
    server backend1.example.com;
    server backend2.example.com;
    server backend3.example.com;
}

server {
    listen 80;
    location / {
        proxy_pass http://backend;
    }
}

# Reverse Proxy Configuration
server {
    listen 80;
    server_name example.com;
    
    location / {
        proxy_pass http://localhost:8080;
        proxy_set_header Host $host;
        proxy_cache my_cache;
    }
}

• Traffic Distribution: Load balancers distribute across multiple servers, while reverse proxies typically forward to a single backend
• SSL Termination: Reverse proxies often handle SSL, while load balancers may pass through encrypted traffic
• Caching: Reverse proxies frequently implement caching, load balancers generally don't
• Protocol Support: Load balancers often work at lower network layers (L4), reverse proxies at application layer (L7)

Consider a load balancer when:

• You need horizontal scaling across identical servers
• High availability is critical
• Simple round-robin or least-connections distribution suffices

Opt for a reverse proxy when:

• You need request/response manipulation
• Caching static content would improve performance
• SSL termination is required
• You need to hide internal server details

Many modern solutions combine both functionalities. For example, AWS ALB (Application Load Balancer) incorporates reverse proxy features:

# Terraform example for AWS ALB with reverse proxy features
resource "aws_lb" "example" {
  name               = "example-lb"
  internal           = false
  load_balancer_type = "application"
  security_groups    = [aws_security_group.lb_sg.id]
  subnets            = aws_subnet.public.*.id

  enable_deletion_protection = true

  access_logs {
    bucket  = aws_s3_bucket.lb_logs.bucket
    prefix  = "test-lb"
    enabled = true
  }

  tags = {
    Environment = "production"
  }
}

Reverse proxies introduce slightly more latency due to additional processing (caching, header manipulation), while load balancers focus on efficient distribution with minimal overhead.

Both can provide security benefits, but in different ways:

• Load balancers: DDoS protection through traffic distribution
• Reverse proxies: Hide backend servers, provide WAF capabilities