Elastic Load Balancer (ELB) checks the service availability of backend servers (ECC instances) by performing health checks. Health checks improve the overall availability of your frontend service, and avoid service impacts caused by exceptions of backend ECC instances.
After you enable the health check function, SELB stops distributing requests to the instance that is discovered unhealthy and restarts forwarding requests to the instance only when it is declared healthy.
If your service is highly sensitive to traffic load, frequent health checks may impact your service. To reduce the impact on your service, you can reduce the health check frequency, increase the health check interval, or change a layer-7 health check to a layer-4 one based on the service conditions. To guarantee the service availability, we do not recommend disabling the health check function.