SAA-C03 Design Cost-Optimized Architectures Practice Question
A startup runs a 24/7 web tier on Amazon EC2 with a stable baseline of 8 instances and a nightly analytics batch job that can resume from checkpoints if interrupted. The company wants to minimize monthly compute cost without hurting the always-on web tier. Which two actions should it take? Select two.
⚠ Common exam trap
Many candidates assume Reserved Instances are always the best choice for any steady workload, but for a part-time batch job, a Savings Plan or Spot is more cost-effective, and they may overlook that Spot Instances with checkpointing are ideal for fault-tolerant, interruptible workloads.
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
✓
Buy a Compute Savings Plan for the steady web tier baseline.
A Compute Savings Plan offers the largest discount (up to 66%) in exchange for a 1- or 3-year hourly spend commitment, and it automatically applies to any EC2 instance family, size, or region. For the stable 8-instance web tier that runs 24/7, this plan provides significant cost savings while maintaining full flexibility to change instance types or even move to containers or Lambda, without affecting the always-on requirement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Buy a Compute Savings Plan for the steady web tier baseline.
Why this is correct
A Compute Savings Plan reduces cost for the predictable baseline while preserving flexibility across instance families and Regions. That fits a 24/7 web tier that is expected to run continuously. It is cheaper than On-Demand for the committed portion and avoids overcommitting to a specific instance family.
- ✗
Buy Standard Reserved Instances only for the nightly analytics batch job.
Why it's wrong here
Reserved Instances are a poor fit for interruptible batch jobs because the job may not run continuously enough to benefit from a reservation. The workload can tolerate interruption, so committing to fixed capacity usually wastes money compared with more flexible pricing.
- ✓
Run the batch job on Spot Instances and checkpoint progress frequently.
Why this is correct
Spot Instances are ideal when interruptions are acceptable and the application can resume from checkpoints. The nightly batch job explicitly supports restart, so Spot lowers compute cost significantly without threatening business continuity for the stable web tier.
- ✗
Move the entire workload to On-Demand Instances for maximum flexibility.
Why it's wrong here
On-Demand offers flexibility, but it is not the lowest-cost option for a steady baseline or for interruption-tolerant processing. The scenario specifically asks to minimize monthly cost, so paying full On-Demand rates for everything is unnecessary.
- ✗
Use Dedicated Hosts for the batch job so the fleet is isolated.
Why it's wrong here
Dedicated Hosts are typically chosen for licensing or compliance isolation requirements, not for minimizing cost. They are usually more expensive than other EC2 purchase options and do not add value to a checkpointed batch workload.
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 SAA-C03 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 SAA-C03 exam.