AWS Certified Solutions Architect - Associate

Explanation

Correct Answer: A

Why Option A is correct:

1. Cost-effectiveness: Standard SQS queues are more cost-effective than FIFO queues. FIFO queues have higher costs and throughput limitations.
2. At-least-once processing: Standard SQS queues provide at-least-once delivery, which meets the requirement to process each request at least once.
3. Security: Using SSE-KMS (AWS Key Management Service) provides strong encryption for sensitive credit card data, which is essential for banking applications.
4. Proper permissions: Adding kms:Decrypt permission to the Lambda execution role is the correct way to grant decryption access.

Why other options are incorrect:

• Option B: FIFO queues are more expensive and provide exactly-once processing, which is overkill for "at least once" requirements. SSE-SQS provides encryption but with SQS-managed keys, which may not meet strict banking security requirements.
• Option C: FIFO queues are more expensive than standard queues and provide exactly-once processing, which exceeds the requirement and increases costs unnecessarily.
• Option D: While standard queues are cost-effective, the permission "encryption key invocation permission" is not a standard AWS permission. The correct permission is kms:Decrypt.

Key AWS Concepts:

• SQS Standard vs FIFO: Standard queues offer best-effort ordering, at-least-once delivery, and higher throughput at lower cost. FIFO queues guarantee exactly-once processing, preserve order, and have lower throughput limits at higher cost.
• SSE-KMS vs SSE-SQS: SSE-KMS uses AWS KMS keys for encryption, providing better security controls and audit trails. SSE-SQS uses SQS-managed keys.
• Lambda Event Source Mapping: Allows Lambda to poll SQS queues and process messages automatically.

For a banking application processing credit card data, security is paramount, but the requirement only specifies "at least once" processing, making standard queues with SSE-KMS the most cost-effective solution.