Azure Load Balancer

A single backend host becomes a bottleneck and a single point of failure. Adding more backends solves only half the problem, because users still need one stable address and the system still needs a way to stop sending traffic to dead targets.

Horizontal scaling created the need for a traffic distribution layer that could keep pace with rapidly changing backend counts. In on-prem environments that often meant dedicated hardware appliances. In cloud environments, the balancing layer also had to become elastic and software-defined so it could adjust as fast as compute did.

Azure Load Balancer combines a frontend IP, a backend pool, balancing rules, and health probes. The frontend accepts traffic, the backend pool holds the actual targets, the rules map ports between them, and the probes keep checking whether each backend is still healthy enough to receive requests.

Azure Load Balancer and Application Gateway both spread traffic, but they operate at different layers. Load Balancer works at the transport layer and does not inspect URLs or headers. Application Gateway and other layer-7 gateways add path-based routing, TLS termination, and web application filtering at the cost of more protocol awareness. When routing depends on URL paths, host headers, or TLS offloading, a layer-7 gateway handles it. When you need raw TCP/UDP distribution across backends without inspecting application content, Load Balancer is the right layer.

A load balancer is the basic entry layer when several backend servers need to behave like one service endpoint. It is common in high-availability server pools and private service tiers where traffic should be spread evenly across healthy targets. It is not enough on its own when routing must depend on URLs, TLS termination rules, or cross-region delivery policy.