DVA-C02 Development with AWS Services Practice Questions

Explanation: Increasing the batch size to 100 allows each Lambda invocation to process up to 100 messages from the SQS queue instead of the current 10. Since the function is idempotent and can handle 100 messages per invocation, this change maximizes the number of messages processed per invocation without altering the reserved concurrency of 5. With a batch size of 100, each of the 5 concurrent invocations can process up to 100 messages, yielding a potential throughput of 500 messages per invocation cycle, which directly reduces the backlog and throttling by consuming messages faster.

Explanation: Increasing the reserved concurrency from 10 to a higher value directly addresses the root cause of throttling. With a batch size of 100, each invocation processes more messages, but the function's reserved concurrency of 10 limits the maximum number of concurrent executions to 10. This means the Lambda service can only invoke the function 10 times at once, regardless of how many messages are in the queue. By raising reserved concurrency, you allow more concurrent invocations to handle the larger batches, reducing throttling and improving throughput.

Explanation: DynamoDB Accelerator (DAX) is a fully managed, highly available, in-memory cache for DynamoDB that delivers up to 10x read performance improvement by reducing response times from milliseconds to microseconds for repeated read queries. By integrating DAX with the Lambda function, the developer can cache the results of frequent DynamoDB queries directly in memory, bypassing the read capacity units and the underlying storage engine, which directly addresses the latency bottleneck shown in the X-Ray trace.

Explanation: Option B is correct because the Amazon States Language (ASL) provides a native Retry field within a Task state definition that allows you to specify retry policies, including a maximum retry count and exponential backoff. This is the intended mechanism for handling transient failures in Step Functions without requiring custom code or external retry logic.

Explanation: A dead-letter queue (DLQ) on the SQS queue ensures that messages that cannot be processed successfully after the configured number of retries (maxReceiveCount) are moved to a separate queue for later analysis or reprocessing. This prevents message loss when the Lambda function fails temporarily, as the SQS queue will continue to receive messages from SNS reliably, and only messages that exceed the retry limit are redirected to the DLQ.