Question: What does DynamoDB Query return?

Answer

DynamoDB Query returns a page of items matching a partition-key value and any sort-key condition, ordered by the sort key. The response can also contain counts, consumed-capacity details and a pagination key.

The main response fields are:

• Items: the returned item attributes, unless you requested COUNT.
• Count: items returned after filtering.
• ScannedCount: items evaluated before filtering.
• LastEvaluatedKey: the key to pass as ExclusiveStartKey for the next page.

Query evaluates up to 1 MB of data or the request's Limit, then applies FilterExpression. Consequently, Limit: 10 does not promise ten returned matches. A page can have an empty Items array and still contain LastEvaluatedKey; continue pagination until that key is absent.

Results use ascending sort-key order by default. Set ScanIndexForward: false to reverse it. Number keys sort numerically; String keys sort by UTF-8 bytes. A Scan has no equivalent ordering guarantee.

ProjectionExpression selects returned attributes but does not reduce read capacity for the same evaluated data. GSI queries can return only projected attributes and are eventually consistent. Low-level clients return DynamoDB type wrappers; document clients return native values.

See query examples and pagination for complete request loops.

Source: AWS Query API.