Application Load Balancer
An Application Load Balancer (ALB) is a Layer 7 load balancer that distributes incoming application traffic across multiple targets, such as EC2 instances, containers, or IP addresses, based on advanced routing rules. It operates at the application layer (HTTP/HTTPS) and can inspect request content to make intelligent routing decisions, such as path-based or host-based routing. ALBs are commonly used in microservices architectures and web applications to improve availability, scalability, and fault tolerance.
Developers should use Application Load Balancers when building modern web applications or microservices that require advanced routing, SSL/TLS termination, or integration with containerized workloads. They are essential for scenarios like A/B testing, blue-green deployments, and handling high-traffic websites, as they provide features like sticky sessions, health checks, and WebSocket support. ALBs are particularly valuable in cloud environments like AWS, where they integrate seamlessly with services like Auto Scaling and ECS.