Load Balancer
Distributing incoming requests across multiple backend instances, so no single one is overwhelmed and a failed one can be routed around.
A load balancer sits in front of a fleet of backend instances and spreads incoming requests across them — by round robin, least-connections, or a hashing scheme — so traffic is shared rather than piling onto one instance. Paired with health checks, it also routes around instances that stop responding, turning a fleet of individually fragile machines into a system that tolerates individual failures.