SAA-C03 Q515 · Serverless

Question

A company has built an application that uses an Amazon Simple Queue Service (Amazon SQS) standard queue and an AWS Lambda function. The Lambda function writes messages to the SQS queue. The company needs a solution to ensure that the consumer of the SQS queue never receives duplicate messages. Which solution will meet this requirement with the FEWEST changes to the current architecture?

Accepted Answer

**Answer B: Delete the standard queue, recreate as FIFO queue with content-based deduplication.**

Step-by-step reasoning:

1. **The core problem**: SQS Standard queues offer **at-least-once delivery**, meaning consumers can receive the same message more than once. There is no configuration on a Standard queue that can guarantee exactly-once delivery.

2. **Why FIFO?**: SQS FIFO queues provide **exactly-once processing**. Within a 5-minute deduplication interval, FIFO queues automatically detect and reject duplicate messages. This is the only SQS queue type that guarantees no duplicates reach the consumer.

3. **Why content-based deduplication?**: FIFO queues require a deduplication mechanism — either a `MessageDeduplicationId` sent with each message, or **content-based deduplication** ena

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📘 Key Concepts

🏗️ Architecture

⚙️ Operations

💰 Cost

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