4.1. Azure Load Balancer

What happens when your application suddenly gets 10x traffic? Without load balancing, either your single server crashes or users wait forever. Azure Load Balancer operates at Layer 4 (TCP/UDP), distributing traffic based on IP address and port—it's the foundation for scalable, highly available applications.

💡 First Principle: Load Balancer doesn't understand HTTP—it sees packets, not requests. This makes it fast and protocol-agnostic but limits it to basic distribution. For HTTP-aware routing, you need Application Gateway or Front Door.

What breaks without proper configuration: Health probes fail and traffic goes to unhealthy instances. SNAT port exhaustion causes intermittent connection failures. Asymmetric routing drops responses.

Think of Load Balancer like a traffic cop at an intersection, directing cars (packets) to different roads (backends) based on simple rules. The cop doesn't know what's inside the cars—just where they're going and how to distribute them evenly. Unlike Application Gateway, it can't route based on the passenger's destination request.