What is the key benefit of using Elastic Load Balancing across multiple Availability Zones?

• A. Distributes traffic across AZs, increasing availability and fault tolerance
• B. Reduces costs by consolidating to fewer instances
• C. Guarantees data replication across regions automatically
• D. Eliminates the need for security groups

Answer: (A)

Distributing traffic across multiple Availability Zones increases availability and fault tolerance. Each AZ is an independent failure domain, so by directing requests to healthy targets in any AZ, the service remains accessible even if one zone experiences an outage or congestion. The load balancer monitors target health and routes traffic only to healthy instances across the zones, effectively spreading load and preventing a single point of failure. This resilience is the main benefit of using Elastic Load Balancing across AZs.

Note that the service doesn't automatically replicate data across regions, and security groups still apply to control access. ELB also doesn’t inherently reduce costs by consolidating instances.