Load Balancing — L4 vs L7

Load balancing distributes traffic for higher availability and performance.

L4 vs L7¶

• L4 — IP + port, fast, content-unaware
• L7 — HTTP headers, URL, cookies, smarter

Algorithms¶

• Round Robin
• Least Connections
• IP Hash (sticky)
• Weighted
• Random

Examples¶

Nginx L4¶

stream { upstream db { server 10.0.1.1:5432; server 10.0.1.2:5432; } server { listen 5432; proxy_pass db; } }

Nginx L7¶

upstream api { server 10.0.1.1:3000; server 10.0.1.2:3000; } server { location /api/ { proxy_pass http://api; } }

Tools¶

• HAProxy — L4/L7, most popular OSS
• Nginx — L7, L4 via stream
• Traefik — cloud-native, auto-discovery
• Cloud LB — AWS ALB/NLB, Azure, GCP

L4 for Speed, L7 for Intelligence¶

L4 for DB/TCP. L7 for HTTP routing and SSL termination.