SAA-C03 Design Cost-Optimized Architectures Practice Question
An application has an unpredictable workload where it receives bursts of traffic for 5 minutes every few hours, followed by periods of complete inactivity. The application is currently running on a small EC2 instance. Which migration strategy would minimize costs for this specific workload?
⚠ Common exam trap
SAA-C03 often tests the misconception that auto scaling or spot instances can achieve the same cost savings as serverless for intermittent workloads, but they still incur costs during idle periods or are not suitable for unpredictable bursts.
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
✓
Refactor the application to run on AWS Lambda.
AWS Lambda is a serverless compute service that charges only for the compute time consumed, measured in milliseconds, and does not charge when the code is not running. For a workload with bursts of traffic for 5 minutes every few hours followed by complete inactivity, Lambda's pay-per-invocation model eliminates costs during idle periods. This makes it the most cost-effective option compared to continuously running or auto-scaled services.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Migrate the application to an AWS Fargate service with an Auto Scaling policy.
Why it's wrong here
Fargate is a serverless container service, but it still has a minimum billing duration and charges for the resources provisioned for the container. For very short 5-minute bursts with long gaps, the overhead of scaling containers up and down still results in higher costs compared to the sub-second billing of Lambda.
- ✓
Refactor the application to run on AWS Lambda.
Why this is correct
Lambda functions are only billed during the time they are executing. For a workload that only runs for a total of 60 minutes a day (5 minutes every few hours), the company would only pay for those 60 minutes of compute, resulting in massive savings over a running EC2 instance.
- ✗
Move the application to an Amazon EC2 T3 instance with Unlimited Credits enabled.
Why it's wrong here
While T3 instances are cheaper than other families, they still charge for every hour the instance is running. Even with burstable credits, the base hourly rate is significantly higher than the cost of a few Lambda invocations, especially since the instance is idle for the majority of the day.
- ✗
Convert the EC2 instance to a Spot Instance to reduce hourly rates.
Why it's wrong here
Using a Spot Instance reduces the hourly cost of the EC2 instance, but the instance would still be running and billing 24/7 to wait for the unpredictable traffic bursts. This remains less cost-efficient than a truly serverless, event-driven model where costs drop to zero during the inactive periods.
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.