Which of the following server roles utilize a heartbeat/polling process? (Choose two.)

Proxy servers forward client requests to destination servers on behalf of clients but do not use heartbeat or polling to monitor node health as a core function of their role.

A certificate authority issues, signs, and revokes digital certificates and does not rely on heartbeat or polling mechanisms to perform its primary function.

Logging servers collect and store log data forwarded by other systems but do not use a heartbeat or polling process as part of their core logging role.

File servers share files and directories across a network to clients but do not inherently use heartbeat or polling mechanisms to fulfill that role.

High-availability clusters use heartbeat signals continuously transmitted between nodes to determine whether each member is alive and reachable; if a node stops sending heartbeats within the configured timeout, the cluster triggers automatic failover to maintain service continuity.

Load balancers use periodic health-check polling to probe each backend server and verify it can accept traffic; servers that fail the health check are removed from the active pool until they recover, preventing requests from being routed to unhealthy nodes.