A load balancer is a networking component that distributes incoming traffic across multiple servers to improve performance, reliability, and scalability. Load balancers prevent any single server from becoming overwhelmed by spreading requests evenly or based on specific rules. They also perform health checks, routing traffic only to healthy instances, and can support advanced features like SSL termination and session affinity.
Why it matters
Without a load balancer, high-traffic applications risk downtime or poor performance when a single server becomes overloaded. Load balancers are fundamental to building horizontally scalable systems and maintaining high availability. They also simplify deployments by allowing rolling updates without disrupting users.
Examples
Using an AWS Application Load Balancer to distribute traffic across EC2 instances, or an NGINX load balancer for distributing traffic to containerized services. Lessons like Load Balancing explore load-balancing strategies.