Active-Passive HA

A high-availability topology in which a primary (active) node handles all production traffic while an identical standby (passive) node remains idle, continuously synchronised with the primary's state. If the primary fails, a failover mechanism — often based on heartbeat signals and VRRP (Virtual Router Redundancy Protocol) or keepalived — promotes the passive node to active and transfers the virtual IP address. Active-passive HA simplifies state management because only one node writes at a time, but wastes the capacity of the standby node. It is common for stateful components such as primary database servers and hardware load balancers.