AWS Certified Developer Associate DVA-C02 Practice Question

A query operation is the correct choice for efficiently retrieving an item using a unique hash key from an Amazon DynamoDB table because a query allows you to specify the hash key and, optionally, a range key to quickly locate the data. Scan operations, in contrast, read every item in a table and filter out results afterwards, which consumes more read capacity and increases latency. Secondary index searches are only necessary when querying on non-primary key attributes, and continuous backup is a durability feature, not related to data retrieval performance.