Health Check

Problem

A load balancer has ten servers. One process has crashed. It shouldn't continue receiving traffic. How can infrastructure know whether an instance is healthy?

Solution — Health Check

Infrastructure periodically checks an endpoint or condition.

Server A → healthy ✓
Server B → healthy ✓
Server C → unhealthy ✗

Traffic can stop going to C.

Core idea: health checks let infrastructure determine whether a workload is functioning.