- A
Use provisioned concurrency for the Lambda function during the expected spike window.
Provisioned concurrency keeps Lambda execution environments initialized before traffic arrives, which reduces cold starts during the predictable busy period. Because the spike is scheduled, the team can pay for the performance benefit only when it is actually needed.
- B
Use Application Auto Scaling or scheduled actions to reduce provisioned concurrency after the spike ends.
Scaling provisioned concurrency back down after the spike avoids paying for idle pre-initialized environments during the low-traffic period. Matching concurrency spend to the business schedule is the cost-optimized part of the design.
- C
Replace the API with a single always-on EC2 instance.
Why wrong: A single EC2 instance removes the serverless elasticity and usually increases operational overhead because the team must patch and maintain the host. It also introduces a weaker availability model than the managed serverless design.
- D
Keep provisioned concurrency permanently high all day and all week.
Why wrong: This wastes money because the pre-warmed Lambda environments would sit idle during the low-traffic hours. The scenario specifically describes a predictable spike, so scheduled provisioning is the better fit.
- E
Disable API Gateway and use direct public internet access to Lambda.
Why wrong: Direct public access is not the normal secure pattern for exposing Lambda and does not address the cost-versus-latency tradeoff. API Gateway provides a managed front door for routing, throttling, and security controls.
Quick Answer
The answer is to use Application Auto Scaling or scheduled actions to reduce provisioned concurrency after the spike ends. This works because Lambda provisioned concurrency for predictable spikes pre-warms a fixed number of execution environments, eliminating cold starts during the 09:00 UTC surge, but leaving that capacity running costs money when traffic drops. By scheduling the provisioned concurrency to scale down immediately after the window, you keep response times fast during the spike without paying for idle capacity the rest of the day. On the SAA-C03 exam, this tests your understanding that provisioned concurrency is a cost-control tool, not just a performance feature—a common trap is thinking you need it always-on or that it replaces Auto Scaling entirely. Remember the mnemonic: “Provision for the peak, schedule to sleep.”
SAA-C03 Design Cost-Optimized Architectures Practice Question
This SAA-C03 practice question tests your understanding of design cost-optimized architectures. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
A serverless checkout API has predictable traffic spikes every weekday at 09:00 UTC and low traffic the rest of the day. The team wants to reduce cost while keeping response times fast during the recurring spike. Which two actions should they take? Select two.
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 provisioned concurrency for the Lambda function during the expected spike window.
Provisioned concurrency initializes a specified number of Lambda execution environments in advance, ensuring no cold starts during traffic spikes. By scheduling provisioned concurrency to activate only during the 09:00 UTC window, the team keeps response times fast without paying for idle capacity the rest of the day.
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.
- ✓
Use provisioned concurrency for the Lambda function during the expected spike window.
Why this is correct
Provisioned concurrency keeps Lambda execution environments initialized before traffic arrives, which reduces cold starts during the predictable busy period. Because the spike is scheduled, the team can pay for the performance benefit only when it is actually needed.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Use Application Auto Scaling or scheduled actions to reduce provisioned concurrency after the spike ends.
Why this is correct
Scaling provisioned concurrency back down after the spike avoids paying for idle pre-initialized environments during the low-traffic period. Matching concurrency spend to the business schedule is the cost-optimized part of the design.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Replace the API with a single always-on EC2 instance.
Why it's wrong here
A single EC2 instance removes the serverless elasticity and usually increases operational overhead because the team must patch and maintain the host. It also introduces a weaker availability model than the managed serverless design.
- ✗
Keep provisioned concurrency permanently high all day and all week.
Why it's wrong here
This wastes money because the pre-warmed Lambda environments would sit idle during the low-traffic hours. The scenario specifically describes a predictable spike, so scheduled provisioning is the better fit.
- ✗
Disable API Gateway and use direct public internet access to Lambda.
Why it's wrong here
Direct public access is not the normal secure pattern for exposing Lambda and does not address the cost-versus-latency tradeoff. API Gateway provides a managed front door for routing, throttling, and security controls.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates might think provisioned concurrency must be always-on to be effective, missing the cost-saving strategy of scheduling it only during predictable spikes.
Trap categories for this question
Scenario analysis trap
This wastes money because the pre-warmed Lambda environments would sit idle during the low-traffic hours. The scenario specifically describes a predictable spike, so scheduled provisioning is the better fit.
Detailed technical explanation
How to think about this question
Provisioned concurrency works by pre-warming a set number of execution environments, which remain initialized and ready to handle requests instantly. When combined with Application Auto Scaling scheduled actions, you can dynamically adjust the provisioned concurrency level to match the spike window, then scale it down to zero or a low baseline afterward, optimizing cost. This approach is especially effective for predictable patterns like daily spikes, as it avoids the latency of cold starts while minimizing idle resource charges.
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.
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 provisioned concurrency for the Lambda function during the expected spike window. — Provisioned concurrency initializes a specified number of Lambda execution environments in advance, ensuring no cold starts during traffic spikes. By scheduling provisioned concurrency to activate only during the 09:00 UTC window, the team keeps response times fast without paying for idle capacity the rest of the day.
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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