SAA-C03 Design High-Performing Architectures Practice Question
A system uses multiple AWS Lambda functions behind different event sources. One Lambda occasionally spikes and causes other Lambdas to be throttled due to shared concurrency limits. Which setting best helps ensure the important Lambda keeps capacity during spikes?
⚠ Common exam trap
Watch out — candidates often confuse Provisioned Concurrency (which reduces cold starts) with Reserved Concurrency (which guarantees capacity), leading them to choose Option C, even though Provisioned Concurrency does not protect against throttling from other functions.
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
✓
Set Reserved Concurrency for the important Lambda function.
Reserved Concurrency guarantees a set number of concurrent executions for a specific Lambda function, isolating it from the account-level concurrency pool. This ensures that the important function always has capacity available, even when other functions spike and consume the shared pool. Without this setting, all functions compete for the same 1,000 concurrent executions (default regional limit), and a spike in one can throttle others.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Increase the function timeout so throttling is less likely.
Why it's wrong here
Timeout affects how long a request can run, not how many requests can run concurrently. Throttling is typically related to concurrency limits rather than time limits. Increasing timeout does not reserve capacity for another function.
When this WOULD be correct
A question where a Lambda function is timing out before completing its task, causing errors or retries, and the requirement is to ensure it finishes processing without failure.
- ✓
Set Reserved Concurrency for the important Lambda function.
Why this is correct
Reserved concurrency allocates a guaranteed amount of concurrent execution capacity to a specific Lambda. This prevents other functions from consuming all concurrency and throttling the important one. If the reserved limit is reached, only that function is throttled, isolating impact.
- ✗
Enable Provisioned Concurrency for every Lambda in the account.
Why it's wrong here
Provisioned Concurrency is useful for reducing cold starts, but it is not primarily a mechanism to guarantee capacity against account-wide spikes. Applying it to every function increases cost. Reserved concurrency is the direct control for prioritizing concurrency capacity.
When this WOULD be correct
A question where the goal is to reduce cold starts for all functions in a latency-sensitive application, and cost is not a primary concern. For example: 'A company wants to ensure all its Lambda functions have minimal latency during unpredictable traffic spikes. Which action should be taken?'
- ✗
Reduce the number of IAM policies attached to the Lambda roles.
Why it's wrong here
Reducing the number of IAM policies attached to Lambda roles does not affect Lambda concurrency throttling in any way. IAM policies govern which AWS actions and resources the function can access, but they have no bearing on the execution capacity available to the Lambda service. Throttling (HTTP 429) occurs when a function exceeds its allocated concurrency — either the account-level limit or per-function Reserved Concurrency — not when permissions are overly broad. Simplifying IAM roles improves security and manageability, but it cannot increase the pool of concurrent executions available to the important function.
When this WOULD be correct
In a scenario where a Lambda function is failing due to permission errors (e.g., AccessDeniedException) and you need to minimize the attack surface, reducing unnecessary IAM policies would be correct to follow the principle of least privilege.
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.
✓Set Reserved Concurrency for the important Lambda function.Correct answer▾
Why this is correct
Reserved concurrency allocates a guaranteed amount of concurrent execution capacity to a specific Lambda. This prevents other functions from consuming all concurrency and throttling the important one. If the reserved limit is reached, only that function is throttled, isolating impact.
✗Increase the function timeout so throttling is less likely.Wrong answer — click to see why▾
Why this is wrong here
Increasing the function timeout does not affect concurrency limits; it only extends the maximum execution duration. Throttling occurs due to hitting the account-level concurrency limit, not timeout.
★ When this WOULD be the correct answer
A question where a Lambda function is timing out before completing its task, causing errors or retries, and the requirement is to ensure it finishes processing without failure.
Why candidates choose this
Candidates may confuse timeout with concurrency, thinking longer execution reduces the chance of being throttled, or believe that throttling is related to execution duration.
✗Enable Provisioned Concurrency for every Lambda in the account.Wrong answer — click to see why▾
Why this is wrong here
Provisioned Concurrency for every Lambda would waste resources and cost, and it does not guarantee that the important Lambda has reserved capacity during spikes; it only pre-warms instances, but all functions still share the same regional concurrency limit.
★ When this WOULD be the correct answer
A question where the goal is to reduce cold starts for all functions in a latency-sensitive application, and cost is not a primary concern. For example: 'A company wants to ensure all its Lambda functions have minimal latency during unpredictable traffic spikes. Which action should be taken?'
Why candidates choose this
Candidates may think Provisioned Concurrency reserves capacity, but it only pre-initializes instances; it does not prevent other functions from consuming the shared pool. The term 'Provisioned' sounds like reserving capacity, leading to confusion with Reserved Concurrency.
✗Reduce the number of IAM policies attached to the Lambda roles.Wrong answer — click to see why▾
Why this is wrong here
Reducing IAM policies does not affect Lambda concurrency limits; it only reduces permissions, which does not prevent throttling from shared concurrency.
★ When this WOULD be the correct answer
In a scenario where a Lambda function is failing due to permission errors (e.g., AccessDeniedException) and you need to minimize the attack surface, reducing unnecessary IAM policies would be correct to follow the principle of least privilege.
Why candidates choose this
Candidates may mistakenly think that reducing IAM policies reduces resource usage or overhead, thereby preventing throttling, but IAM policies have no impact on concurrency limits.
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?”
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.