Question

A CloudOps engineer deploys an Application Load Balancer (ALB) across three Availability Zones, but each AZ contains a different number of registered targets: AZ-a has 8 instances, AZ-b has 4, and AZ-c has 2. Users report that instances in AZ-c are experiencing significantly higher CPU utilization than instances in the other zones. What is the most likely cause of this uneven load?

Accepted Answer

Cross-zone load balancing has been disabled on the ALB, so traffic is split evenly per AZ, forcing the 2 instances in AZ-c to handle a full one-third of all requests.

Answer

The ALB distributes traffic evenly across all healthy targets regardless of AZ because cross-zone load balancing is always enabled and cannot be disabled for ALBs.

Answer

The ALB is using least-outstanding-requests routing, which always sends more traffic to zones with fewer instances.

Answer

Sticky sessions are enabled, which forces all traffic into the AZ with the fewest instances.