A load balancer is a device or software application that distributes network or application traffic across multiple servers. It helps in optimizing the performance and availability of a service or application by distributing the workload evenly among the servers. Load balancers typically work at the network layer (Layer 4) or the application layer (Layer 7) of the OSI model.
Load balancers perform health checks on the servers to ensure they are functioning properly and can handle the incoming traffic. They monitor the server's capacity, response time, and other metrics to determine the optimal distribution of requests.
Load balancers improve the scalability of applications by adding or removing servers dynamically based on the current load. They also provide high availability by automatically detecting and redirecting traffic from failed or overloaded servers to healthy servers.