SAP-C02 FIFO Queue Practice Question
A company is designing a serverless event-driven application using AWS Lambda. The application processes messages from an Amazon SQS queue. The team needs to ensure that messages are processed in order and exactly once. Which THREE steps should be taken?
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
✓
Configure the Lambda event source mapping to use the FIFO queue.
To achieve message ordering and exactly-once processing with Lambda and SQS, you must use a FIFO queue (option B) because FIFO queues preserve the order of messages. Additionally, enable the queue's content-based deduplication or provide a deduplication ID (option E) to prevent duplicate messages from being processed. Finally, set the Lambda function's reserved concurrency to 1 (option D) to ensure that only one instance of the function processes messages at a time, maintaining the order. Option A (batch window 0) is incorrect because it would cause Lambda to wait longer, but does not help with ordering. Option C (standard queue) does not guarantee ordering or deduplication.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable Lambda function's batch window to 0.
Why it's wrong here
Batch window does not affect ordering.
- ✓
Configure the Lambda event source mapping to use the FIFO queue.
Why this is correct
The event source mapping must be configured to read from the FIFO queue.
- ✗
Use a standard SQS queue.
Why it's wrong here
Standard queues do not guarantee ordering or exactly-once.
- ✓
Set the Lambda function's reserved concurrency to 1.
Why this is correct
Reserved concurrency of 1 prevents parallel processing, preserving order.
- ✓
Use a FIFO SQS queue with a message deduplication ID.
Why this is correct
FIFO queues guarantee order and exactly-once with deduplication.
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 |
Go deeper
Related to this question
About these practice questions
This SAP-C02 question is part of Courseiva's 1,660-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 by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAP-C02 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 SAP-C02 exam.