SAA-C03 Design Resilient Architectures Practice Question
A global e-commerce enterprise runs its checkout workflow using AWS Lambda functions integrated with Amazon API Gateway. During flash sales, traffic spikes cause downstream payment APIs to timeout, leading to lost transactions and frustrated customers. The solutions architect needs to redesign the architecture to decouple the frontend from the payment processor and ensure no transaction requests are lost. What should the architect do?
⚠ Common exam trap
SAA-C03 often tests the misconception that increasing Lambda timeout/memory or adding caching solves decoupling problems, when the real requirement is durable buffering with SQS.
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
✓
Integrate an Amazon SQS FIFO queue between API Gateway and the downstream payment processing Lambda functions.
Integrating an Amazon SQS FIFO queue between API Gateway and the payment Lambda decouples the frontend from the downstream payment processor, buffering requests during traffic spikes so no transaction is lost. FIFO queues preserve order and provide exactly-once processing, which is critical for payment transactions. The Lambda functions can then poll the queue at a controlled rate, preventing downstream timeouts.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure API Gateway to cache responses using an Amazon ElastiCache Redis cluster deployed in multi-AZ mode.
Why it's wrong here
Caching responses in ElastiCache Redis stores API Gateway replies, so a timed-out payment request is still lost rather than queued for later processing. Caching suits read-heavy, repeatable GET workloads where identical responses can be served without recomputation, not transactional payment writes requiring guaranteed delivery.
- ✓
Integrate an Amazon SQS FIFO queue between API Gateway and the downstream payment processing Lambda functions.
Why this is correct
An SQS FIFO queue buffers checkout requests when payment Lambdas are throttled, decoupling API Gateway from the processor so requests persist rather than being lost to timeouts. FIFO ordering and exactly-once processing preserve transaction sequence, directly meeting the no-lost-transactions requirement during flash-sale spikes.
- ✗
Increase the timeout and memory allocation of the API Gateway integration and the AWS Lambda functions.
Why it's wrong here
Raising Lambda memory and integration timeouts only extends how long a request waits before failing; it adds no buffer, so requests still vanish when the payment API stays saturated. Larger timeouts and memory suit steady, predictable loads needing faster execution, not absorbing sudden spikes without loss.
- ✗
Use AWS Step Functions with standard workflows to execute the payment processing steps sequentially.
Why it's wrong here
Step Functions standard workflows orchestrate and retry steps but do not buffer incoming requests; API Gateway still invokes them synchronously, so a spike overwhelms the payment API before execution begins. Standard workflows suit long-running, auditable multi-step orchestration, not decoupling bursty producers from consumers.
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
This SAA-C03 question is part of Courseiva's 149-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam 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.