DynamoDB scan/query performance regression in v3.928.0

[juhr]

Checkboxes for prior research

• I've gone through Developer Guide and API reference
• I've checked AWS Forums and StackOverflow.
• I've searched for previous similar issues and didn't find any solution.

Describe the bug

Scans and queries in @aws-sdk/client-dynamodb v3.928.0 and above are significantly slower in AWS Lambda compared to v3.927.0. For example, scanning ~8,000 items takes ~1,500ms in v3.927.0 but 6–10 seconds in v3.928+ versions. This regression appears in all versions starting with 3.928.0; earlier versions perform normally.

Regression Issue

• Select this option if this issue appears to be a regression.

SDK version number

@aws-sdk/client-dynamodb@3.927.0 (fast, baseline), @aws-sdk/client-dynamodb@3.928.0 and above (slow)

Which JavaScript Runtime is this issue in?

Node.js

Details of the browser/Node.js/ReactNative version

nodejs20.x

Reproduction Steps

Background:
Table contains ~8,000 items.
Average item size is ~1,100 KB.
Regression observed in @aws-sdk/client-dynamodb v3.928.0 and above.

Query example

import { DynamoDBClient } from "@aws-sdk/client-dynamodb";
import { DynamoDBDocument } from "@aws-sdk/lib-dynamodb";

const client = DynamoDBDocument.from(new DynamoDBClient({ region: "eu-north-1" }));

async function fetchAllQueryItems() {
  const params = {
    TableName: "YourTableName",
    KeyConditionExpression: "pk = :pk",
    ExpressionAttributeValues: { ":pk": "exampleKey" },
  };

  let items = [];
  let lastEvaluatedKey;
  do {
    if (lastEvaluatedKey) params.ExclusiveStartKey = lastEvaluatedKey;

    const response = await client.query(params);
    items = items.concat(response.Items || []);
    lastEvaluatedKey = response.LastEvaluatedKey;
  } while (lastEvaluatedKey);

  console.log("Total items fetched:", items.length);
}

fetchAllQueryItems().catch(console.error);

Observed Behavior

The code takes about 3-5 times longer to execute in v3.928.0 and above.

Expected Behavior

Fetching items should be as quick as it were while using v3.927.0 and below.

Possible Solution

No response

Additional Information/Context

No response

[kuhe]

(#7523)

A deserialization performance fix that should help with the particular structural profile of DynamoDB Items was released in https://github.com/aws/aws-sdk-js-v3/releases/tag/v3.940.0.

It should appear on NPM shortly, please give it a try: https://www.npmjs.com/package/@aws-sdk/client-dynamodb/v/3.940.0.

If this version doesn't help with the performance, I'll likely need some more detailed information such as the exact item shape.