When performing a minimal effort upgrade, what will happen to the network traffic?

All connections that were initiated before the upgrade will be handled by the active gateway. According to the Check Point documentation1, a minimal effort upgrade is a procedure that allows you to upgrade each Security Gateway individually, without affecting the cluster operation. The active gateway continues to handle the traffic while the standby gateway is upgraded, and then they switch roles. This way, there is no network downtime and no need to synchronize the cluster members before or after the upgrade1. However, some connections may be dropped during the switch-over, so it is recommended to use a connectivity upgrade or a zero downtime upgrade for mission-critical environments2.

References: : Best Practices - Security Gateway Performance - Check Point Software : Checkpoint Cluster Firmware Upgrade - Check Point CheckMates