Exam AWS Certified DevOps Engineer - Professional DOP-C02 topic 1 question 168 discussion

It's C, here is a reference: https://docs.aws.amazon.com/lambda/latest/dg/with-sqs.html#services-sqs-batchfailurereporting

C does not prevent multiple message processing

The visibility timeout determines how long SQS will "hide" a message after Lambda begins processing it. The key here is ensuring that the message is not available for another Lambda function invocation until the current one completes successfully. The visibility timeout should be at least as long as the Lambda function's maximum processing time, ensuring that the same message is not processed again while it is being handled.

To prevent Lambda from processing a message multiple times, you can either configure your event source mapping to include batch item failures in your function response, or you can use the DeleteMessage API to remove messages from the queue as your Lambda function successfully processes them. To avoid reprocessing successfully processed messages in a failed batch, you can configure your event source mapping to make only the failed messages visible again. This is called a partial batch response. To turn on partial batch responses, specify ReportBatchItemFailures for the FunctionResponseTypes action when configuring your event source mapping. This lets your function return a partial success, which can help reduce the number of unnecessary retries on records. Source: https://docs.aws.amazon.com/lambda/latest/dg/services-sqs-errorhandling.html#services-sqs-batchfailurereporting

"Implementing partial batch responses When "Lambda function encounters an error while processing a batch, all messages"... "become visible in the queue"... "including messages that Lambda processed successfully." "...your function can end up processing the same message several times. "To avoid reprocessing successfully processed messages in a failed batch" "configure your event source mapping to make only the failed messages visible again." "To turn on partial batch responses, specify ReportBatchItemFailures for the FunctionResponseTypes action when configuring your event source mapping." "This lets your function return a partial success, which can help reduce the number of unnecessary retries on records." https://docs.aws.amazon.com/lambda/latest/dg/services-sqs-errorhandling.html

C doesn't address the "maximize the scalability of Lambda" while B addresses both, while batch size is 1, you either fail or success

To avoid reprocessing successfully processed messages in a failed batch, you can configure your event source mapping to make only the failed messages visible again. This is called a partial batch response. To turn on partial batch responses, specify ReportBatchItemFailures for the FunctionResponseTypes action when configuring your event source mapping. This lets your function return a partial success, which can help reduce the number of unnecessary retries on records. https://docs.aws.amazon.com/lambda/latest/dg/with-sqs.html#services-sqs-batchfailurereporting

answer C

https://docs.aws.amazon.com/lambda/latest/dg/with-sqs.html#services-sqs-batchfailurereporting

C is correct. We need ReportBatchItemFailures to return only failed items A: batch window is the interval process time B: batch size is the size of the job D: queue visibility timeout is about re-process

https://docs.aws.amazon.com/lambda/latest/dg/with-sqs.html#services-sqs-batchfailurereporting

Lambda process messages in batches. If one message in the batch fails the whole batch considered failed and all messages in the batch return to the queue. For example if batch has 10 messages and message 5 and 7 failed to get processed, all 10 messages will return to the queue. So, successfully processed messages can get processed again. Now to prevent this to happen you have two ways (used to be one) 1. Write your code in a way to identify processed messages and delete them manually from SQS. 2. Partial batch response that returns only the messages that were failed to be processed (supported since Dec 2021). References: https://docs.aws.amazon.com/lambda/latest/dg/with-sqs.html https://docs.aws.amazon.com/lambda/latest/dg/with-sqs.html#services-sqs-batchfailurereporting

C is correct.

B is correct