Application Load Balancer (ALB)

An Application Load Balancer (ALB) is a critical component in modern cloud and distributed application architectures, operating at Layer 7 (the application layer) of the OSI model. Its primary function is to intelligently distribute incoming HTTP and HTTPS traffic across multiple target resources, such as virtual machines, containers, and IP addresses. Unlike traditional load balancers, an ALB performs sophisticated content-based routing, directing requests based on granular criteria like URL paths, host headers, HTTP methods, and query string parameters, thereby optimizing resource utilization and improving user experience.

In the context of cybersecurity, an ALB serves as a vital security control within cloud architectures. It centralizes SSL/TLS termination, offloading cryptographic processing from backend servers and simplifying certificate management. This creates a strategic enforcement point where security policies—often integrated with Web Application Firewalls (WAFs)—can be applied before traffic reaches sensitive backend infrastructure. Additionally, an ALB continuously performs health checks on registered targets, ensuring requests are only routed to healthy instances. This combination of intelligent routing, encryption management, and health monitoring significantly enhances the availability, resilience, and overall security posture of cloud-hosted applications.