SAP-C02 Continuous Improvement for Existing Solutions Practice Question

• A.Create multiple Lambda functions each processing a subset of the queue.
• B.Decrease the reserved concurrency to force the function to process messages more efficiently.
• ✓ C.Increase the reserved concurrency for the Lambda function.
• D.Increase the batch size of the SQS event source mapping.

Why C: Increasing the reserved concurrency from 5 to a higher value allows the Lambda function to handle more concurrent invocations, directly reducing throttling errors. Option A is incorrect because each Lambda function has its own concurrency limit; adding more functions does not increase the concurrency of a single function. Option B is incorrect because decreasing reserved concurrency would worsen throttling. Option D is incorrect because increasing the batch size increases the number of messages processed per invocation but does not increase the number of concurrent invocations, so it does not address throttling caused by concurrency limits.

• A.Increase the function's maximum thread count.
• ✓ B.Increase the reserved concurrency to 20.
• C.Create additional SQS queues and distribute messages.
• D.Increase the SQS batch size to 100.

Why B: Increasing the reserved concurrency to 20 allows more Lambda functions to run simultaneously, enabling more messages to be processed in parallel. This is the fastest way to increase throughput because it directly increases the number of concurrent executions handling messages from the SQS queue. Option A is incorrect because Lambda does not have a configurable maximum thread count. Option C is incorrect because the SQS batch size is limited to a maximum of 10, not 100. Option D is incorrect because creating additional queues would require significant application changes and does not directly increase the processing capacity of the existing Lambda function.

• A.Use a DynamoDB table to store unique message IDs and check for duplicates before processing.
• B.Set the Lambda function's reserved concurrency to a higher value to prevent throttling.
• C.Increase the visibility timeout of the SQS queue to 30 minutes.
• ✓ D.Change the SQS queue to a FIFO queue and enable content-based deduplication.

Why D: Exactly-once processing is achieved by using an SQS FIFO queue with content-based deduplication. FIFO queues guarantee that a message is delivered exactly once and consumers receive messages in order. Lambda supports SQS FIFO as an event source, though it has lower throughput limits. Option A (DynamoDB-based idempotency) also works but adds complexity and cost. Option B (increasing reserved concurrency) only helps with scaling but does not prevent duplicates if a message is processed but the function fails after processing. Option C (increasing visibility timeout) delays reprocessing but does not guarantee exactly-once if the function is throttled or fails.