SOA-C02 Cost and Performance Optimization Practice Question
A company runs a development Amazon EC2 instance that is only used during business hours (9 AM to 5 PM). The SysOps administrator wants to reduce compute costs. Which action should be taken?
⚠ Common exam trap
Candidates often confuse cost reduction strategies and choose Reserved Instances (Option B) for any recurring workload, failing to recognize that a development instance with limited daily usage does not justify a long-term commitment and that stopping the instance when idle is the most direct way to eliminate compute costs.
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
✓
Schedule the instance to automatically stop during off-hours and start before business hours
The instance is only needed during business hours (9 AM to 5 PM), so automatically stopping it during off-hours and starting it before business hours eliminates compute charges for idle time. Stopped instances incur no EC2 instance running costs (only storage and EBS volume costs), directly reducing the compute bill. AWS Instance Scheduler or a simple cron-based Lambda function can enforce this schedule reliably.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use On-Demand instances
Why it's wrong here
On-Demand pricing avoids long-term commitments but charges per second for every running instance, with no discount for idle time. Leaving this development instance running 24/7 means paying for the entire week even though it is only needed for an 8-hour business day. Simply selecting On-Demand is not a cost-reduction strategy; the charges only disappear when you actively stop the instance during off-hours, which is exactly what an automated schedule provides.
- ✗
Use a Reserved Instance
Why it's wrong here
A Reserved Instance requires a 1- or 3-year commitment and is billed for every clock hour in the term, regardless of whether a matching instance is running. This workload is active for roughly 40 hours per week, only about 24% of the week, so a Reserved Instance would charge you for thousands of unused hours and make the solution more expensive than On-Demand with scheduled stops. Reserved Instances are economical only for steady-state, always-on workloads, not for a development environment that is idle most of the time.
- ✓
Schedule the instance to automatically stop during off-hours and start before business hours
Why this is correct
Using Amazon EventBridge Scheduler or the AWS Instance Scheduler solution, you can automate stopping the instance at the end of the business day and starting it again before the next workday begins. EC2 billing is per-second while the instance is in the running state, so stopping it during evenings and weekends eliminates most compute charges while retaining the EBS volumes, configuration, and data. The schedule ensures the environment is available when developers arrive and requires no manual intervention, directly matching compute spend to actual usage.
- ✗
Use a Spot instance
Why it's wrong here
Spot Instances can provide discounts of up to 90%, but AWS can reclaim that capacity at any time when it needs the resources back, typically with only a two-minute warning. A development environment that must be reliably available during business hours cannot tolerate this kind of preemption, since a Spot interruption would terminate the instance mid-session and potentially lose unsaved work. Even though Spot is inexpensive, it is a poor fit for a workload that has strict availability requirements and would need complex checkpointing or failover mechanisms to be usable.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.