What happens to standby hosts while they are in standby mode?

When standby hosts are in standby mode, they are not engaged in processing any requests or maintaining active data copies. Specifically, they do not contain any customer data nor do they accept queries during this state. Standby hosts are kept in a mode that allows them to take over in the event of a failure of the primary host, but while in standby mode, their main role is to remain inactive, ensuring that they can be quickly activated if needed.

This design allows for high availability and ensures that system resources are not being consumed unnecessarily while the primary instance is operational. It also means that the standby hosts will have to be synchronized with the primary instance to ensure they can effectively take over in case of a failover, but during actual standby, they do not serve any functions that involve managing data or queries.