Relational DynamoDB: When DynamoDB Stops Being Simple &#xA; Let&rsquo;s be clear about something upfront: if you&rsquo;re using DynamoDB as a simple key-value store—storing&#xA;session data, caching API responses, or managing user preferences—you don&rsquo;t need any of this. Just&#xA;use the AWS SDK directly. Store your items, retrieve them by ID, and move on with your life. &#xA; But the moment…