Systems Design Concepts Practice Test

Health checks verify that each backend server can actually handle requests. The load balancer periodically probes the servers, and if a server fails the probes consistently, it is taken out of the traffic rotation so new requests aren’t sent to it. This automatic removal of unhealthy servers keeps the service available by avoiding failed nodes, and once a server recovers, it can rejoin the rotation. The other options aren’t the primary role of health checks. Checking client device health isn’t something the load balancer does. DNS failover is a separate mechanism for directing traffic at a higher level, not about monitoring individual backends. SSL certificate validity isn’t the core function of health checks, though some systems can monitor cert expiry, it’s not what the health check primarily accomplishes.