How to notify failed DynamoDB sales above a price threshold with least effort?

The requirement is to notify only when TransactionStatus is failed AND Price exceeds a threshold, with the LEAST development effort. The optimal pattern is:

• Enable DynamoDB Streams (already done).
• Create an event source mapping from the stream to an AWS Lambda function.
• Use Lambda event filtering to restrict invocations to records where dynamodb.NewImage.TransactionStatus.S = "failed" and dynamodb.NewImage.Price.N satisfies a numeric condition such as ["numeric": [">", threshold]].
• Inside the tiny Lambda handler, publish the filtered payload to an Amazon SNS topic.

This matches Option A. Lambda event filtering is performed by the service before the function is invoked, so the function code stays minimal — just an SNS publish call — which directly satisfies the "least development effort" constraint.

Why the other options are wrong:

• Option B also uses Lambda + SNS, but performs the filtering inside the handler code. This works, but it requires writing, testing, and maintaining conditional logic in the function, so it is more development effort than using native event filtering.
• Option C claims you can map DynamoDB Streams directly to an SNS topic and rely on SNS filter policies. DynamoDB Streams does not support SNS as a direct event source destination; it supports Lambda, Kinesis Data Streams, and a few other targets. Therefore this design is not feasible.
• Option D suggests using a CloudWatch alarm on DynamoDB Streams data. CloudWatch alarms operate on metrics, not on individual stream records or attribute values, so they cannot evaluate per-record conditions like "TransactionStatus = failed and Price > X". This option is architecturally incorrect.

Community comments reinforce this: candidates who initially leaned toward C or D corrected themselves after reviewing the Lambda event filtering documentation for DynamoDB, confirming that A is the only valid and minimal-effort solution.