DVA-C02 Development with AWS Services Practice Question
A developer is creating an AWS Lambda function to process events from an Amazon SQS queue. The function must process each message exactly once and in order. Which SQS queue type should the developer use?
⚠ Common exam trap
Watch out — candidates often confuse the 'exactly-once' and 'in-order' requirements with Standard queues, assuming they can achieve this with idempotent processing, but Standard queues explicitly do not guarantee order and can deliver duplicates.
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
✓
FIFO queue.
FIFO queue. FIFO (First-In-First-Out) queues guarantee exactly-once processing and preserve the order of messages, which is required by the use case. Standard queues offer at-least-once delivery and do not guarantee order, making them unsuitable for this requirement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Standard queue.
Why it's wrong here
Amazon SQS Standard queues offer maximum throughput and best-effort ordering, but they do not guarantee the order in which messages are delivered. Furthermore, messages are delivered "at least once," meaning duplicate messages can be received. This makes Standard queues unsuitable for scenarios requiring strict message ordering or exactly-once processing, as the Lambda function might process events redundantly or out of sequence.
- ✓
FIFO queue.
Why this is correct
Amazon SQS FIFO (First-In-First-Out) queues are designed to guarantee message ordering and exactly-once processing. They ensure that messages are processed in the exact order they are sent and prevent duplicates from being delivered to the consumer, thanks to message deduplication IDs and message group IDs. This makes FIFO queues ideal for applications where the sequence of operations and the prevention of duplicate processing are critical for data integrity.
- ✗
Dead-letter queue.
Why it's wrong here
A Dead-Letter Queue (DLQ) is a secondary queue used to isolate messages that a consumer, such as an AWS Lambda function, fails to process successfully after a specified number of retries. Its purpose is to store problematic messages for later analysis or reprocessing, rather than serving as the primary source for initial event ingestion. Therefore, a DLQ is not the appropriate type of queue to configure as the main event source for a Lambda function.
- ✗
Delay queue.
Why it's wrong here
A Delay queue is not a distinct queue type but rather a feature applied to an SQS queue that makes newly sent messages invisible for a specified duration, up to 15 minutes. This functionality is designed to postpone the processing of messages, allowing time for other dependencies or operations to complete. However, it does not inherently provide guarantees for message ordering or exactly-once processing, which are often critical for reliable event-driven architectures.
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 DVA-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 DVA-C02 exam.