SOA-C02 Cost and Performance Optimization Practice Question
A company runs a stateless web application on a fleet of Amazon EC2 instances behind an Application Load Balancer. The application experiences predictable traffic patterns: high during business hours and low at night. The SysOps administrator wants to reduce compute costs without affecting performance during peak hours. Which action should the administrator take?
⚠ Common exam trap
The trap here is assuming that any Auto Scaling policy will automatically optimize cost, when scheduled scaling is specifically designed for predictable traffic patterns and avoids over-provisioning.
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 policy for the Auto Scaling group that increases the desired capacity before business hours and decreases it after hours.
The application has predictable traffic patterns, so scheduled scaling is the most efficient way to match capacity to demand. It increases instances before business hours and decreases them after, ensuring performance during peak times while reducing cost during off-peak hours. Reserved Instances would commit to peak capacity around the clock, target tracking is reactive and less precise for known schedules, and Spot Instances risk interruptions that could affect 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.
- ✓
Create a scheduled scaling policy for the Auto Scaling group that increases the desired capacity before business hours and decreases it after hours.
Why this is correct
Scheduled scaling allows you to scale the Auto Scaling group based on a schedule, such as increasing capacity at 8 AM and decreasing at 8 PM. Because the traffic pattern is predictable, scheduled scaling ensures that enough instances are running during peak hours and reduces cost by terminating unnecessary instances at night. This is the most cost-effective and performance-safe approach for a stateless application with known traffic patterns.
- ✗
Use Spot Instances for the entire fleet and enable termination protection.
Why it's wrong here
Spot Instances can reduce costs significantly, but they can be interrupted when AWS needs the capacity back, which is not suitable for a production web application that must remain available. Termination protection does not prevent Spot interruptions; it only prevents accidental termination via the console or API. Spot is appropriate for fault-tolerant, stateless workloads that can handle interruptions, but this application requires consistent performance during peak hours, so Spot alone is not the best choice.
- ✗
Purchase a 1-year All Upfront Reserved Instance for the maximum number of instances needed during peak hours.
Why it's wrong here
Reserved Instances provide a discount for steady-state usage, but they require a commitment for the entire term regardless of actual usage. If you purchase RIs for the peak number of instances, you pay for those instances even at night when they are not needed, which increases cost. For a variable workload with predictable peaks, Reserved Instances are not the optimal cost-saving measure; they are better suited for continuously running instances.
- ✗
Configure a target tracking scaling policy with a CPU utilization target of 50%.
Why it's wrong here
Target tracking scaling adjusts capacity based on a metric such as CPU utilization, which is reactive and may lag behind sudden changes in traffic. While it can handle predictable patterns, it does not proactively scale before the traffic increase, so there may be a brief period of under-provisioning or over-provisioning. For a known schedule, scheduled scaling is more precise and cost-effective because it scales exactly when needed without waiting for metric thresholds to be breached.
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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
This SOA-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 SOA-C02 exam.