SOA-C02 Networking and Content Delivery Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  Configure the ALB to use subnets in at least two Availability Zones

  Why this is correct

  To provide high availability, the Application Load Balancer (ALB) must be enabled in multiple Availability Zones by associating it with at least one subnet in each AZ. The ALB service creates a load balancer node in each enabled AZ, allowing it to route traffic to targets in those AZs and to continue serving requests if one AZ fails. Without multi-AZ subnet configuration, the ALB and its single node become a single point of failure, negating the resilience of having multiple EC2 instances across AZs. This is the foundational action required to meet fault-tolerance requirements.

• ✗

  Add more EC2 instances in the same Availability Zone

  Why it's wrong here

  Adding more EC2 instances in the same Availability Zone does not eliminate the single point of failure at the Availability Zone level. All of those instances share the same physical infrastructure, power, and network connectivity; if that AZ becomes unavailable, the application goes down regardless of how many instances are running. This approach only increases capacity within one failure domain and does nothing to improve resilience or make the ALB itself highly available. The requirement is to spread risk across distinct AZs, not to scale within a single zone.

• ✗

  Replace the ALB with a Network Load Balancer (NLB)

  Why it's wrong here

  Replacing the ALB with a Network Load Balancer (NLB) does not solve the root cause because an NLB is also a regional service that must be configured with subnets in at least two Availability Zones to achieve high availability. If the NLB is attached only to a single AZ, it still represents a single point of failure, just as the current ALB does. Additionally, the application is a web application that likely relies on layer-7 features such as path-based routing, host-based routing, or sticky sessions, which an NLB does not natively provide. Thus, this change introduces unnecessary complexity and potential feature loss without addressing the multi-AZ requirement.

• ✗

  Enable cross-zone load balancing on the ALB

  Why it's wrong here

  Cross-zone load balancing on an ALB enables the load balancer to distribute incoming traffic evenly across all registered instances in all enabled Availability Zones, but it does not take effect unless the ALB itself is already attached to subnets in multiple AZs. If the ALB is only enabled in one AZ, its nodes exist only in that AZ, and it cannot route traffic to instances in other AZs, regardless of the cross-zone setting. Cross-zone load balancing is a distribution policy that works after the ALB spans multiple AZs; it is not a substitute for making the load balancer infrastructure multi-AZ. Enabling this setting alone leaves the ALB as a single point of failure.

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