Backend
What is Load Balancer?
A component that distributes incoming traffic across multiple servers to improve availability, throughput, and fault tolerance.
Definition
A load balancer sits in front of a pool of servers and spreads incoming connections across them using strategies such as round-robin, least-connections, or consistent hashing. Layer 4 balancers route raw TCP/UDP; layer 7 balancers like NGINX, HAProxy, and AWS ALB inspect HTTP and can route by path, header, or cookie. They also run health checks, eject failing instances, and terminate TLS. Because no single server handles all traffic, the system survives instance failures and scales horizontally by simply adding nodes to the pool.