Health checks are a mechanism used by load balancers to monitor the status of registered targets, such as EC2 instances, ensuring that traffic is only routed to healthy targets [citation:6][citation:10].
Health checks are a critical feature of Elastic Load Balancing (ELB) that monitor the health of your registered targets (e.g., EC2 instances). The load balancer sends periodic requests to each target on a configured cadence. If a target fails to respond within a specified timeout or responds with an error code, the load balancer marks it as unhealthy and stops routing traffic to it. Once the target becomes healthy again, the load balancer resumes routing traffic to it [citation:6][citation:10].