SOA-C02 Cost and Performance Optimization Practice Question
A company runs a web application on Amazon EC2 instances that run 24/7. The application has a predictable and steady load. The SysOps administrator wants to minimize compute costs while ensuring the required capacity is always available. Which purchasing option should be used?
⚠ Common exam trap
Many exam-takers choose On-Demand Instances for simplicity, overlooking that Reserved Instances provide substantial cost savings for predictable, always-on workloads without any risk of interruption.
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
✓
Reserved Instances
Reserved Instances (RIs) are the correct choice because the workload runs 24/7 with a predictable and steady load. By committing to a 1- or 3-year term, the company can achieve a significant discount (up to 72%) compared to On-Demand pricing, while ensuring capacity is always available. This aligns with the goal of minimizing compute costs without sacrificing 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.
- ✗
On-Demand Instances
Why it's wrong here
On-Demand Instances offer maximum flexibility with no upfront commitment and per-second billing, but they carry the highest hourly rate of all EC2 purchasing options. For a predictable 24/7 web application, running On-Demand throughout the year results in substantially higher total cost compared to a Reserved Instance. While appropriate for short-term, spiky, or undefined workloads, it is not the most cost-optimal choice for a continuous, steady-state infrastructure.
- ✓
Reserved Instances
Why this is correct
Reserved Instances are a billing discount that requires a 1- or 3-year commitment to a specific instance family, region, and operating system. In exchange for that commitment, you receive up to a 72% discount off the On-Demand hourly rate, depending on the payment option (All Upfront, Partial Upfront, or No Upfront). For an always-on web application with predictable compute needs, this significantly lowers the monthly cost, making Reserved Instances the most cost-effective choice among the available options.
- ✗
Spot Instances
Why it's wrong here
Spot Instances allow you to use spare EC2 capacity at discounts of up to 90% off On-Demand prices, but they can be terminated by AWS with only a two-minute warning when capacity is needed elsewhere. An always-on web application must maintain high availability and cannot tolerate sudden interruptions, so running it entirely on Spot Instances would risk downtime and failed user requests. Even with Spot Fleet or a mixed strategy, Spot is unsuitable as the primary purchasing option for a 24/7 production workload.
- ✗
Dedicated Hosts
Why it's wrong here
Dedicated Hosts provide a physical server dedicated solely to your use, enabling you to bring your own server-bound software licenses and meet compliance or regulatory requirements. You are billed per host rather than per instance, which is typically far more expensive than shared tenancy pricing. Since the scenario describes a standard web application with no licensing or compliance constraints, Dedicated Hosts introduce unnecessary cost and administrative overhead without providing relevant benefits.
Go deeper
Related to this question
About these practice questions
One of 1,169 original SOA-C02 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more way this is tested on SOA-C02
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company runs a web application on a fleet of Amazon EC2 instances that operate 24/7 with a steady and predictable load. The SysOps administrator wants to minimize compute costs while ensuring the required capacity is always available. Which EC2 purchasing option should the administrator use?
easy- ✓ A.Reserved Instances
- B.Spot Instances
- C.On-Demand Instances
- D.Dedicated Hosts
Why A: Reserved Instances (RIs) are the correct choice because the workload runs 24/7 with steady, predictable load. RIs provide a significant discount (up to 72%) over On-Demand pricing in exchange for a one- or three-year commitment, ensuring cost minimization while guaranteeing capacity availability in the specified Availability Zone.
JA
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.