- A
Deploy the job on EC2 instances and keep them running continuously for the daily schedule.
Why wrong: Always-on EC2 instances increase cost and do not minimize operational overhead for short-lived jobs.
- B
Use AWS Lambda triggered by a schedule (for example, EventBridge) to run the report at the required time.
Lambda runs on demand and charges for execution time, aligning spend with actual job runtime and reducing ops.
- C
Run the job in an RDS database using stored procedures scheduled by the database engine.
Why wrong: RDS is not designed for general scheduled compute workloads like daily report generation.
- D
Use an Auto Scaling group with a fixed minimum size of one instance and disable scaling.
Why wrong: A fixed-size Auto Scaling group still requires instance management and does not fully match runtime-based billing.
SAA-C03 Design Cost-Optimized Architectures Practice Question
This SAA-C03 practice question tests your understanding of design cost-optimized architectures. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An internal team runs a report-generation job once per day. It typically finishes in a few minutes, and even on its slowest days it still completes in under 15 minutes. The team wants to reduce operational overhead and pay primarily for actual runtime instead of keeping servers running 24/7. Which AWS approach best matches these goals?
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
Use AWS Lambda triggered by a schedule (for example, EventBridge) to run the report at the required time.
AWS Lambda, triggered by Amazon EventBridge (CloudWatch Events), is ideal for short-lived, infrequent jobs like this daily report. It eliminates idle server costs by running only when invoked, and the 15-minute execution timeout comfortably covers the job's maximum runtime. This serverless approach directly reduces operational overhead and aligns with a pay-per-use cost model.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Deploy the job on EC2 instances and keep them running continuously for the daily schedule.
Why it's wrong here
Always-on EC2 instances increase cost and do not minimize operational overhead for short-lived jobs.
When this WOULD be correct
If the job required a persistent, stateful environment (e.g., large local storage, specific OS configurations) or needed to run multiple times per day with unpredictable latency demands, EC2 instances running continuously would be appropriate.
- ✓
Use AWS Lambda triggered by a schedule (for example, EventBridge) to run the report at the required time.
Why this is correct
Lambda runs on demand and charges for execution time, aligning spend with actual job runtime and reducing ops.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Run the job in an RDS database using stored procedures scheduled by the database engine.
Why it's wrong here
RDS is not designed for general scheduled compute workloads like daily report generation.
When this WOULD be correct
If the question required processing large datasets directly within a database (e.g., complex aggregations on terabytes of data) and the team already had a running RDS instance for other purposes, using stored procedures could be efficient without additional compute overhead.
- ✗
Use an Auto Scaling group with a fixed minimum size of one instance and disable scaling.
Why it's wrong here
A fixed-size Auto Scaling group still requires instance management and does not fully match runtime-based billing.
When this WOULD be correct
A question where a workload requires a single EC2 instance to always be available (e.g., a legacy application that cannot be containerized or serverless) and must automatically recover from failure, with the goal of high availability rather than cost optimization.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The SAA-C03 exam frequently reuses these exact scenarios with slightly different constraints.
✓Use AWS Lambda triggered by a schedule (for example, EventBridge) to run the report at the required time.Correct answer▾
Why this is correct
Lambda runs on demand and charges for execution time, aligning spend with actual job runtime and reducing ops.
✗Deploy the job on EC2 instances and keep them running continuously for the daily schedule.Wrong answer — click to see why▾
Why this is wrong here
Keeping EC2 instances running 24/7 incurs costs for idle time, contradicting the goal of paying primarily for actual runtime when the job completes in under 15 minutes daily.
★ When this WOULD be the correct answer
If the job required a persistent, stateful environment (e.g., large local storage, specific OS configurations) or needed to run multiple times per day with unpredictable latency demands, EC2 instances running continuously would be appropriate.
Why candidates choose this
Candidates may default to EC2 for any compute workload without considering serverless alternatives, overlooking the cost and operational overhead of idle instances.
✗Run the job in an RDS database using stored procedures scheduled by the database engine.Wrong answer — click to see why▾
Why this is wrong here
Running the job as stored procedures in RDS would still require a running database instance 24/7, incurring costs for idle time, and does not align with the goal of paying primarily for actual runtime.
★ When this WOULD be the correct answer
If the question required processing large datasets directly within a database (e.g., complex aggregations on terabytes of data) and the team already had a running RDS instance for other purposes, using stored procedures could be efficient without additional compute overhead.
Why candidates choose this
Candidates might think that using RDS stored procedures eliminates the need for separate compute resources, overlooking that the database instance itself must remain running continuously, incurring costs regardless of job execution.
✗Use an Auto Scaling group with a fixed minimum size of one instance and disable scaling.Wrong answer — click to see why▾
Why this is wrong here
An Auto Scaling group with a fixed minimum size of one instance keeps an EC2 instance running 24/7, which incurs costs for idle time and does not reduce operational overhead or pay-per-use runtime.
★ When this WOULD be the correct answer
A question where a workload requires a single EC2 instance to always be available (e.g., a legacy application that cannot be containerized or serverless) and must automatically recover from failure, with the goal of high availability rather than cost optimization.
Why candidates choose this
Candidates may think Auto Scaling automatically reduces costs, but a fixed minimum of one instance means the instance never scales in, so it runs continuously, failing to meet the 'pay primarily for actual runtime' requirement.
Analysis generated from the official SAA-C03blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may assume EC2 or Auto Scaling is needed for any scheduled job, overlooking that Lambda's 15-minute timeout and serverless pricing perfectly suit short, infrequent tasks, while the 'pay primarily for actual runtime' requirement explicitly points away from always-on compute.
Detailed technical explanation
How to think about this question
Lambda functions have a maximum execution timeout of 15 minutes (900 seconds), which matches the job's worst-case runtime. Under the hood, Lambda uses Firecracker microVMs for isolation, and EventBridge cron expressions (e.g., 'cron(0 2 * * ? *)') trigger the function once daily. In a real-world scenario, if the job needed more than 15 minutes, you would consider AWS Fargate or Batch instead, but here the timeout is sufficient.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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 |
What to study next
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FAQ
Questions learners often ask
What does this SAA-C03 question test?
Design Cost-Optimized Architectures — This question tests Design Cost-Optimized Architectures — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use AWS Lambda triggered by a schedule (for example, EventBridge) to run the report at the required time. — AWS Lambda, triggered by Amazon EventBridge (CloudWatch Events), is ideal for short-lived, infrequent jobs like this daily report. It eliminates idle server costs by running only when invoked, and the 15-minute execution timeout comfortably covers the job's maximum runtime. This serverless approach directly reduces operational overhead and aligns with a pay-per-use cost model.
What should I do if I get this SAA-C03 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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