SAA-C03 Design High-Performing Architectures Practice Question
A startup runs a stateless web application on Amazon EC2 instances behind an Application Load Balancer. Traffic is steady during the day but drops to almost zero overnight, and the team wants to reduce compute cost without manual intervention or a service interruption. Which action should the team take?
⚠ Common exam trap
The trap here is choosing Spot Instances purely for cost when the scenario's real requirement is matching capacity to a known daily traffic curve without risking reclamation.
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
✓
Create a scheduled scaling action on an Auto Scaling group that reduces the desired capacity at night and restores it each morning.
The workload has a predictable daily pattern, which is exactly what scheduled scaling on an Auto Scaling group is designed for. Reducing desired capacity overnight and restoring it in the morning lowers compute spend while the group and load balancer keep the application available. Connection draining on the ALB ensures in-flight requests finish before instances terminate, so users see no interruption.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Replace the Auto Scaling group with a single large EC2 instance and use Elastic Load Balancing health checks.
Why it's wrong here
Consolidating onto one instance removes the horizontal scaling that the ALB and Auto Scaling group provide, creating a single point of failure and a capacity ceiling. It also does not reduce overnight cost meaningfully because the instance keeps running. This trades availability and elasticity for no real savings.
- ✓
Create a scheduled scaling action on an Auto Scaling group that reduces the desired capacity at night and restores it each morning.
Why this is correct
Scheduled scaling adjusts the desired capacity of an Auto Scaling group at defined times, so the fleet can shrink overnight when traffic is near zero and grow before the morning peak. Because the group manages instance lifecycle and the ALB drains connections, there is no service interruption. This matches a predictable daily pattern and removes manual intervention.
- ✗
Attach an Amazon EBS volume with higher IOPS to each instance to reduce the number of instances needed.
Why it's wrong here
A stateless web application is not constrained by EBS IOPS, so provisioning faster volumes adds cost without reducing the instance count. The overnight idle period remains unchanged, and the fleet still runs at day capacity. This option does not align with the elastic compute pattern the scenario requires.
- ✗
Switch to Spot Instances for the entire fleet and rely on capacity-optimized allocation.
Why it's wrong here
Spot Instances reduce compute cost but can be reclaimed with a two-minute interruption notice, so running the entire fleet on Spot risks capacity loss. It also does not address the overnight idle period directly; the instances still run unless scaling acts. A mixed or diversified Spot strategy would be safer, but it is not the best fit for a predictable daily cycle.
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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
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