DOP-C02 Resilient Cloud Solutions 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.

• ✗

  Launch both instances in the same Availability Zone.

  Why it's wrong here

  Placing both EC2 instances in the same Availability Zone defeats the purpose of high availability. Even if the ALB can route to multiple targets, those targets share the same physical infrastructure (power, network, cooling) and failure domain. If that single AZ experiences an outage, the ALB has no healthy targets in another AZ, so the entire application goes down. This design creates a single point of failure at the AZ level and does not satisfy the availability requirement.

• ✓

  Place the instances in different Availability Zones behind the ALB.

  Why this is correct

  An Application Load Balancer is a regional, layer-7 service that can route traffic to healthy targets across multiple Availability Zones. By placing EC2 instances in different AZs and registering them in the ALB's target group, the ALB automatically performs health checks and reroutes traffic away from unhealthy instances or entirely failed AZs. This design ensures that if one AZ becomes unavailable, the ALB continues to serve requests using instances in the other AZ. The combination of cross-zone load balancing and health-based target removal makes this the industry-standard resilient architecture.

• ✗

  Configure Route 53 latency-based routing to each instance.

  Why it's wrong here

  Latency-based routing in Route 53 simply directs users to the endpoint with the lowest network latency; it does not evaluate the health of the EC2 instances or AZs. If the lowest-latency instance becomes unhealthy, Route 53 will continue sending traffic to it, causing connection failures or timeouts. Additionally, latency-based routing requires each instance to have a public IP address and is not designed for failover—it lacks health checks and automatic traffic shifting. Thus, while it can optimize performance, it does not provide the availability guarantee needed.

• ✗

  Configure Route 53 failover routing with health checks pointing to each instance.

  Why it's wrong here

  Route 53 failover routing with health checks can indeed redirect traffic when an instance fails, but it works at the DNS level and introduces latency due to DNS TTL caching by clients. Using this as the primary high-availability mechanism forces each EC2 instance to be publicly exposed and managed via individual DNS records, which conflicts with a private, auto-scaling architecture. The ALB already provides integrated health checks, automatic target group registration, and rapid cross-AZ failover without any DNS propagation delay. Adding Route 53 failover is redundant and typically slower, making it a less effective solution.

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