What does Cross Zone Load Balancing ensure for instances in different availability zones?

The concept of Cross Zone Load Balancing is designed to ensure that traffic is evenly distributed across all the available instances in different availability zones. When enabled, this feature allows a load balancer to distribute incoming application traffic across instances located in multiple availability zones. This means that if you have instances in several zones, regardless of their respective load, the traffic is allocated evenly across all zones, leading to optimal resource utilization and improved fault tolerance.

By achieving an even distribution of traffic, the load balancer helps to prevent any single zone from becoming a bottleneck, which in turn enhances the overall performance and scalability of the application. This is particularly important in high-availability architectures, as it ensures that even if one availability zone experiences issues, the instances in other zones can still handle the traffic effectively without being overwhelmed.

Other options, such as equal distribution of Amazon RDS traffic, increased security for data transmission, and improved session reliability for users, do not directly relate to the primary function of Cross Zone Load Balancing, which specifically focuses on the equitable distribution of incoming traffic across instances in multiple availability zones.