Why DynamoDB Query not Returning any Items in Low-Level Client?

[waleedshkt]

Discussed in #6847

^{Originally posted by waleedshkt January 24, 2025}
This may sound ridiculous to ask. But on a serious note, I am putting in an item in DynamoDB successfully using PutItemCommand. I confirm it by scanning for items in AWS console.

But on querying it, the QueryCommand is not returning any item (empty array)

Primary key is comprised of _type partition key and uid sort key. The sort key is hash (string)

Here is my code for querying to get al items with specific partition key:

import { marshall, unmarshall } from "@aws-sdk/util-dynamodb";
import { DynamoDBClient, QueryCommand } from "@aws-sdk/client-dynamodb";

const client = new DynamoDBClient({...credentials});
const res = await client.send(new QueryCommand({
   TableName: SOME_NAME,
   ScanIndexForward: false,
   KeyConditionExpression: "#_type = :type AND uid > :uid",
   ExpressionAttributeValues: marshall({
      ":type": "apple",
      ":uid": "0"
   }),
   ExpressionAttributeNames: {
      "#_type": "_type"
   },
}));

if(res) {
   return res.items.map(item => unmarshall (item));
}else{
   throw Error("Failed to fetch");
}

The item in dynamodb to query against has primary key: _type = 'apple' and uid = 'dh46dhdj3jdhd738'

What is possibly wrong? Is using an uncommon underscore prefix in partition key causing any breakage on dynamodb side?

Using

@aws-sdk/util-dynamodb@3.716.0
@aws-sdk/client-dynamodb@3.716.0
ap-south-1

Update:
I even checked it with ConsistentRead set to true. But the items are just not returning despite being able to do so in console with same query.

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