SAP-C02 Continuous Improvement for Existing Solutions Practice Question
A company runs a web application on EC2 instances behind an Application Load Balancer. Users report intermittent 503 errors. CloudWatch logs show the ALB's healthy host count occasionally drops to zero during traffic spikes. Which design change should a solutions architect implement to improve availability?
⚠ Common exam trap
The trap is picking a cost or deployment option (Reserved Instances, instance refresh) when the symptom — healthy host count dropping to zero — clearly points to a capacity and scaling responsiveness problem.
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
✓
Increase the size of the Auto Scaling group and adjust scaling policies.
The ALB's healthy host count dropping to zero during traffic spikes indicates the Auto Scaling group cannot provision enough healthy instances fast enough to handle the load, causing the ALB to return 503 errors. Increasing the group size (raising the minimum/desired capacity) and tuning scaling policies (lower thresholds, shorter cooldowns, larger step adjustments) ensures more instances are available and scale-out happens sooner, improving availability.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable EC2 instance refresh for the Auto Scaling group.
Why it's wrong here
Instance refresh replaces instances to pick up new launch template or AMI settings; it does not add capacity, so hosts still drop to zero during spikes. It is tempting because refresh improves fleet consistency, and it would be correct when rolling out a configuration or image update across an Auto Scaling group.
- ✓
Increase the size of the Auto Scaling group and adjust scaling policies.
Why this is correct
The healthy host count hitting zero means capacity is exhausted before new instances register. Enlarging the Auto Scaling group and tuning its policies keeps sufficient healthy targets behind the ALB during spikes, preventing the 503s caused by having no available backend.
- ✗
Purchase Reserved Instances for the existing EC2 fleet.
Why it's wrong here
Reserved Instances only change billing, not capacity or health-check behaviour, so the healthy host count still hits zero during spikes. They are tempting because they cut compute cost for steady, predictable workloads, but this scenario needs elasticity, not a discount.
- ✗
Replace the ALB with a larger Network Load Balancer.
Why it's wrong here
A Network Load Balancer operates at layer 4 and cannot evaluate HTTP health checks or route by path, so unhealthy targets stay in rotation. It suits ultra-low-latency TCP or UDP traffic, not an HTTP application needing layer 7 health monitoring.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
This SAP-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SAP-C02 exam.