SOA-C02 Reliability and Business Continuity 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.

• ✗

  Remove the load balancer and use Route 53 weighted routing to distribute traffic.

  Why it's wrong here

  Removing the load balancer and relying on Route 53 weighted routing is incorrect because weighted records simply direct DNS queries to endpoints based on assigned weights; they do not continuously verify instance health or reroute traffic when an instance or Availability Zone fails. Even if you attach Route 53 health checks to the weighted records, DNS time-to-live (TTL) values and client DNS caching can delay failover by minutes, making it unsuitable for maintaining high availability for an interactive web application without an always-on load balancer acting as the frontend.

• ✗

  Launch all instances in a single Availability Zone to reduce latency.

  Why it's wrong here

  Launching all instances in a single Availability Zone introduces a single point of failure; if that zone experiences an outage, the application will become completely unavailable, failing to meet the reliability requirement for an entire Availability Zone failure. While this configuration would minimise network latency between instances, which is beneficial for certain tightly coupled applications or specific database access patterns, the primary objective here is high availability across zones, not inter-instance latency optimisation.

• ✓

  Configure the Auto Scaling group to launch instances in three Availability Zones.

  Why this is correct

  Configuring the Auto Scaling group to launch instances in three Availability Zones is the correct approach because it distributes the web application across separate physical data centers within the Region. The Auto Scaling group manages instance health and automatically replaces unhealthy or failed instances in the remaining AZs, while the Application Load Balancer routes traffic only to healthy instances across all three zones. This design ensures that if an entire AZ experiences an outage, the load balancer shifts traffic to instances in the other AZs, keeping the application available and meeting the reliability requirement.

• ✗

  Use a Network Load Balancer instead of an Application Load Balancer.

  Why it's wrong here

  Switching to a Network Load Balancer instead of an Application Load Balancer would not solve the availability problem because both load balancer types are regional services that must have at least one subnet with an availability zone, and neither provides built-in protection against an Availability Zone failure unless the backend instances themselves are distributed across multiple zones. The choice between ALB and NLB is driven by the traffic layer and features needed, such as HTTP routing or static IP addresses, not by zone redundancy. Since the existing instances remain in a single (or insufficient number of) Availability Zones, a Network Load Balancer would still have a single point of failure for the backend capacity.

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