SAA-C03 Design High-Performing Architectures Practice Question
A latency-sensitive API is implemented with AWS Lambda. During traffic ramp-ups, users sometimes experience slow responses due to cold starts. The team wants to ensure fast initialization for a baseline level of concurrent requests. Which AWS feature should they use?
⚠ Common exam trap
A common mix-up: candidates confuse 'provisioned concurrency' with 'reserved concurrency' (which only caps concurrency, not pre-warms) or think that reducing the function timeout or adding S3 triggers can somehow mitigate cold starts.
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
✓
Lambda provisioned concurrency
Lambda Provisioned Concurrency keeps a specified number of execution environments initialized and ready to respond immediately, eliminating cold starts for those concurrent requests. This directly addresses the latency-sensitive API requirement during traffic ramp-ups by ensuring fast initialization for a baseline level of concurrency.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Lambda provisioned concurrency
Why this is correct
Lambda provisioned concurrency pre-initializes a specified number of execution environments and holds them in a ready state, so requests are served immediately without the initialization delay that causes cold starts. By configuring a baseline concurrency, you ensure that latency-sensitive APIs experience consistent response times even during traffic spikes, as new environments are warmed ahead of actual invocations.
- ✗
Increase reserved instances for EC2
Why it's wrong here
Reserved Instances are a billing model for Amazon EC2 that offer discounted capacity, but they do not apply to AWS Lambda's serverless execution model. Lambda manages its own fleet of execution environments, and reserved capacity for EC2 has no effect on when a Lambda function's container is initialized or reused. Thus, this option neither warms Lambda environments nor mitigates cold start latency for your API.
- ✗
Enable S3 event notifications for every request to the API
Why it's wrong here
S3 event notifications trigger when objects are created/updated in S3. They are not part of Lambda cold start mitigation for API invocations and would add unnecessary event-processing complexity without warming Lambda in a reliable way.
- ✗
Decrease the function timeout to reduce execution variability
Why it's wrong here
Changing the timeout affects how long Lambda can run before terminating, not whether the runtime environment is pre-initialized. It does not address cold start latency and may cause failures for requests that require more time.
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.