A solutions architect is designing an asynchronous application to validate credit card data for a bank. The application must be secure and must process each request at least once. Which solution is the MOST cost-effective?
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Correct answer: Use AWS Lambda event source mapping. Set Amazon Simple Queue Service (Amazon SQS) standard queues as the event source. Use AWS Key Management Service (SSE-KMS) for encryption. Add the kms:Decrypt permission for the Lambda execution role..
Why this is the answer
The most cost-effective solution uses SQS Standard queues because they are cheaper than FIFO queues and meet the "at least once" processing requirement. Asynchronous processing does not require strict ordering. SSE-KMS is a valid encryption choice, and adding kms:Decrypt to the Lambda execution role is the correct way to grant decryption permissions.
Using SQS FIFO queues (options 2 and 3) is more expensive and unnecessary for this asynchronous, "at least once" processing scenario, as FIFO queues guarantee strict message ordering and exactly-once processing, which are not required here. Option 4 incorrectly states "encryption key invocation permission for the Lambda function"; the correct permission is kms:Decrypt for the Lambda execution role.