Reserved Instances for Steady-State Workloads
An application runs on c5.xlarge EC2 instances 24 hours a day, 7 days a week in us-east-1. The workload is stable and will not change instance type for at least 12 months. The team wants to reduce compute costs by 30 to 40 percent compared to On-Demand pricing. Which purchasing option achieves this with the lowest financial risk?
Quick Answer
The answer is to purchase a 1-year Standard Reserved Instance for c5.xlarge in us-east-1 with All Upfront or Partial Upfront payment. This is correct because a Standard Reserved Instance provides a 30-40% discount over On-Demand pricing for a steady-state workload that runs 24/7, and the one-year term matches the stable, predictable nature of the workload without over-committing. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this question tests your ability to match purchasing options to workload characteristics, specifically distinguishing Standard RIs from Convertible RIs (which offer flexibility but at a lower discount) and Spot Instances (which risk interruption). A common trap is choosing a three-year term for a deeper discount, but that increases financial risk if the workload changes. For a reserved instance for always-on workload, remember the rule: steady-state equals Standard RI, and match the term to the commitment window. Memory tip: “Standard for steady, Convertible for change.”
⚠ Common exam trap
Many exam-takers choose the 3-year Convertible RI (Option D) for its higher discount percentage, overlooking the fact that the longer commitment and unnecessary flexibility introduce greater financial risk for a stable, unchanging workload.
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
✓
Purchase a 1-year Standard Reserved Instance for c5.xlarge in us-east-1 with All Upfront or Partial Upfront payment
A 1-year Standard Reserved Instance (RI) with All Upfront or Partial Upfront payment offers a 30-40% discount over On-Demand pricing for a stable, always-on workload. This option provides the lowest financial risk because it commits to a fixed instance type and region for only one year, matching the workload's stable nature without the flexibility premium of Convertible RIs or the interruption risk of Spot Instances.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Purchase a 1-year Standard Reserved Instance for c5.xlarge in us-east-1 with All Upfront or Partial Upfront payment
Why this is correct
A 1-year Standard RI matches the 12-month stability horizon and delivers 30–40 percent savings versus On-Demand. All Upfront provides the deepest discount; Partial Upfront reduces the upfront cash requirement with a slightly lower overall saving. The 1-year commitment limits risk compared to a 3-year commitment for an uncertain future period.
- ✗
Use Spot Instances with an interruption tolerance of 5 minutes for the workload
Why it's wrong here
Spot Instances can be interrupted with 2-minute warning when EC2 capacity is needed. A 24/7 production workload that cannot tolerate interruption is not suitable for Spot Instances. Spot is appropriate for fault-tolerant, flexible workloads such as batch processing or stateless web tiers.
- ✗
Enable EC2 Auto Scaling with a target tracking policy to scale down to zero instances during off-peak hours
Why it's wrong here
The workload runs 24/7 and does not have off-peak hours. Scaling to zero is not applicable for a continuously running application. Auto Scaling with target tracking optimizes capacity for variable workloads, not for reducing costs on a continuously required instance.
- ✗
Purchase a 3-year Convertible Reserved Instance to maximize the discount percentage
Why it's wrong here
A 3-year commitment maximizes discount but introduces risk over a 36-month period for a workload only confirmed stable for 12 months. The question asks for the lowest financial risk — a 1-year RI minimizes the commitment period while still achieving the target savings.
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 |
Go deeper
Related to this question
About these practice questions
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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 batch processing job every night that takes exactly 2 hours to complete. The job is time-sensitive and cannot tolerate interruptions. The SysOps administrator needs to minimize compute costs for the Amazon EC2 instances used during this job. The job runs every day and has predictable resource requirements. Which purchasing option should the administrator choose?
medium- ✓ A.Reserved Instances (Standard)
- B.Spot Instances
- C.On-Demand Instances
- D.Dedicated Hosts
Why A: A Standard Reserved Instance is the best choice because the job runs every night for exactly 2 hours with predictable resource requirements, making it ideal for a 1-year or 3-year commitment that provides a significant discount (up to 72%) over On-Demand pricing. Since the job cannot tolerate interruptions, Reserved Instances offer capacity reservation and cost savings without the risk of termination that Spot Instances carry.
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.