The correct choice is DynamoDB because it provides native change capture and can invoke Lambda functions on item inserts updates and deletes.

DynamoDB exposes DynamoDB Streams which captures item level inserts updates and deletes and integrates natively with AWS Lambda through event source mappings enabling near real time serverless processing. Streams retain records for up to 24 hours and you can scale consumers to process changes efficiently so DynamoDB can be the system of record while also driving event driven Lambda workflows.

Kinesis is a streaming platform and not a database so it does not serve as the system of record for orders. Kinesis can ingest and process streams but the question asks you to pick a database that emits change events natively.

RDS is a managed relational database and it does not provide native change streams that automatically trigger Lambda. To capture changes from RDS you would need additional tools such as AWS DMS or custom CDC pipelines which adds complexity.

ElastiCache is an in memory cache and not suitable as the system of record for order data and it does not emit change events to Lambda.

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