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Advanced 20 min readModule: Module 2: Load Balancing (L4 vs L7) & Reverse Proxies

Load Balancers (L4 vs L7) & Consistent Hashing

Distribute traffic across server pools using Round Robin, Least Connections, and Consistent Hashing.

What You Will Learn in This Lesson

  • Layer 4 (TCP/UDP IP hash) vs Layer 7 (HTTP path, headers, cookies)
  • Load balancing algorithms: Weighted Round Robin, Least Connections
  • Consistent Hashing rings to prevent cache stampedes during node scaling

Introduction & Core Concept

Load balancers distribute incoming network traffic across a group of backend servers to maximize throughput, minimize response time, and avoid overload on any single server.
WHY DOES THIS MATTER IN THE REAL WORLD?

Consistent Hashing ensures that when a cache node crashes, only 1/N of keys are remapped rather than invalidating 100% of the cache.

Layer 7 HTTP Route Routing

nginx
nginx
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upstream api_servers {
    least_conn;
    server 10.0.0.1:4000;
    server 10.0.0.2:4000;
}
server {
    listen 80;
    location /api/ {
        proxy_pass http://api_servers;
    }
}

Line-by-Line Technical Breakdown

1Reverse proxies also provide SSL termination, gzip compression, and DDoS filtering.

Try It Yourself (Interactive Editor)

Modify the code in real-time and click Run to test live browser output and console logs.

Intelligent Code Runner & Live Sandbox[NGINX]
NGINX SOURCE EDITOR
Interactive Live Code

Industry Best Practices & Professional Standards

  • Deploy load balancers in active-passive pairs with Virtual IP (VRRP) to prevent LB SPOFs.

Lesson Summary & Core Takeaways

  • Load balancing distributes concurrency and guarantees high availability.