SAA-C03 Design Cost-Optimized Architectures Practice Question
A company is migrating a legacy application to AWS. The application requires a relational database with very infrequent and unpredictable usage—sometimes it is not used for days, and then it sees a burst of activity for an hour. Which database configuration is most cost-effective?
⚠ Common exam trap
SAA-C03 often tests the misconception that any RDS or Aurora option is equally cost-effective for intermittent workloads, when in fact only Aurora Serverless automatically scales down or pauses to avoid charges during idle periods.
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
✓
Amazon Aurora Serverless.
Amazon Aurora Serverless is designed for workloads with intermittent, unpredictable, or infrequent usage. It automatically starts up, shuts down, and scales capacity based on application demand, so you only pay for the database capacity consumed during active periods. For an application that is idle for days and then bursts for an hour, this eliminates the cost of provisioning a always-on instance, making it the most cost-effective relational database configuration.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Amazon RDS for MySQL on a T3-medium instance.
Why it's wrong here
Using a standard RDS instance results in continuous hourly charges. Even with a small T3 instance, the company would be paying for the database 24/7, even during the days when there is no activity. This leads to significant wasted expenditure compared to a serverless model.
- ✓
Amazon Aurora Serverless.
Why this is correct
Aurora Serverless is the most cost-effective choice because it scales to zero capacity (in v1) or a very low baseline (in v2) when there is no traffic. You are only billed for Aurora Capacity Units (ACUs) when the database is actually processing requests, perfectly aligning costs with the 'unpredictable' usage pattern.
- ✗
Amazon Aurora with a Reserved Instance.
Why it's wrong here
Reserved Instances offer a discount for a committed term but are designed for steady-state workloads that run 24/7. For a database that is unused for days at a time, the cost of the reservation—even with the discount—is much higher than the on-demand serverless charges for occasional bursts.
- ✗
Amazon RDS with Multi-AZ enabled.
Why it's wrong here
Multi-AZ is a high-availability feature that doubles the number of instances and nearly doubles the cost. It provides no cost-optimization benefits and is unnecessary for a legacy application with infrequent usage where a slight delay in scaling or recovery might be acceptable.
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 |
About these practice questions
Courseiva writes every SAA-C03 question from scratch — 149 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
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 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.