Two servers are to be configured for high availability in a cluster. Both servers will be running applications at the same time. This feature is know as:

Round robin is a load balancing scheduling algorithm that distributes incoming requests sequentially across servers, but it is not the term that describes a clustering mode where all nodes run applications simultaneously.

Heartbeat refers to the periodic health-check signal exchanged between cluster nodes to detect failures, not to the operational mode in which both nodes actively serve workloads.

In an active/active cluster configuration, every node is online and actively processing requests at the same time, which distributes the workload across both servers and maximizes resource utilization. If one node fails, the surviving node continues to handle the full load, satisfying the high availability requirement without a failover delay from a standby state. This is distinct from active/passive, where one node sits idle until the active node fails.

Active/passive clustering means one node is the primary active node while the other remains on standby and only takes over if the active node fails, meaning they do not both run applications simultaneously.