SAA-C03 Design High-Performing Architectures Practice Question
A retail API uses EC2 instances behind an ALB. CPU is consistently high during peak traffic, and request latency rises. What should be configured? The design must avoid adding custom operational scripts.
⚠ Common exam trap
Many exam-takers confuse VPC endpoints (which enable private connectivity) with actual scaling mechanisms, or assume that disabling health checks is a quick fix for latency, when in fact it degrades reliability and does not address the underlying capacity issue.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Auto Scaling policy based on an appropriate CloudWatch metric
An Auto Scaling policy based on a CloudWatch metric like CPUUtilization or ALB TargetResponseTime can dynamically add or remove EC2 instances to match demand. This directly addresses the high CPU and rising latency during peak traffic without requiring custom scripts, as the scaling actions are fully managed by AWS. The ALB distributes traffic across the scaled instances, reducing per-instance load and improving response times.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Auto Scaling policy based on an appropriate CloudWatch metric
Why this is correct
An Auto Scaling policy that uses a CloudWatch metric such as Average CPUUtilization immediately addresses the symptom: when CPU load rises beyond a threshold, it launches additional EC2 instances to distribute incoming ALB traffic, and when utilization falls it terminates excess instances. This is the standard, automated horizontal-scaling mechanism for a retail API and directly matches the need to accommodate fluctuating CPU load without manual intervention.
- ✗
S3 Object Lock
Why it's wrong here
S3 Object Lock provides a write-once-read-many (WORM) model, preventing objects from being deleted or overwritten for a specified retention period (e.g., for compliance or ransomware protection). It operates entirely on data objects stored in Amazon S3 and has no connection to compute fleets, instance lifecycle, or CPU usage of API servers. Consequently, enabling Object Lock cannot add processing capacity or reduce CPU pressure on the EC2 instances behind the ALB.
- ✗
A VPC endpoint for CloudWatch only
Why it's wrong here
A VPC endpoint for CloudWatch only creates a private network path from the VPC to the CloudWatch service, avoiding internet traversal for metrics and logs. This improves security and potentially lowers network latency and data-transfer costs, but it alters only how instances reach CloudWatch APIs. It does not change the number of EC2 instances, their CPU capacity, or the way the ALB distributes requests, so it leaves a high-CPU condition unaffected.
- ✗
Disable health checks
Why it's wrong here
Disabling the ALB health checks means the load balancer will stop verifying the ability of an instance to receive and respond to traffic, so requests can continue to be routed to failed or degraded instances. That not only forces users to experience timeouts and 5xx errors, it also keeps unhealthy instances in rotation and prevents Auto Scaling from detecting them for replacement, making the CPU load worse on the remaining healthy instances. It is an anti-pattern that reduces availability and reliability rather than increasing capacity.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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