Amazon web services – ValidationException: The provided key element does not match the schema/ Express js with DynamoDB

I have been stuck for quite a while trying to fix the ValidationException error. I am using Javascript v3 and DynamoDBClient.

Things I have done:

• Made sure the aws credentials can be used with my standalone react application (still in the process of self-learning AWS)
• Did a simple ScanCommand to bring over data from DynamoDB to frontend (works)
• Verified that data is passed to the backend from frontend sucessfully (works)

This is my DynamoDB table design:

The table name is Users,

My credential and access key: (root user not created user)

For backend, I am using Express js:

import Express from "express";
import cors from "cors";
import dotenv from "dotenv";
import path from "path";
import bodyparser from "body-parser";
import {DynamoDBClient} from "@aws-sdk/client-dynamodb";
import {GetCommand} from "@aws-sdk/lib-dynamodb";
import {fromEnv} from "@aws-sdk/credential-providers"; // This is required
import bcrypt from 'bcrypt';

const aws_creds = path.join(process.cwd(), "../", "env/", "awsbackend.env")
console.log("ENV File: " + aws_creds.toString());

// Load environment variable into process environment
dotenv.config({path: aws_creds});

// NOTE: This will only work after loading to process environment
console.log(process.env.backendport);
console.log(process.env.AWS_ACCESS_KEY_ID);

var capstone_proj = Express();

capstone_proj.use(cors());

capstone_proj.use(bodyparser.json());

var creds = fromEnv(); // No matter what, this is required

let DBnoSQL = new DynamoDBClient({
  region: process.env.region,
  credentials: creds,
});

capstone_proj.post('/login', async (req, res) => {
  const { Usrname, Password } = req.body;

  console.log(req.body);

  try {
    const command = new GetCommand({
      TableName: "Users",
      Key : {
         "Username": {S: Usrname}
      }
    });
    const data = await DBnoSQL.send(command);

    if (!data.Item) {
      return res.status(404).json({ error: 'Wrong login credentials' });
    }

    const isPasswordValid = await bcrypt.compare(
      Password,
      data.Item.Password_Hash.S,
    );

    if (isPasswordValid) {
      return res.status(200).json({ message: "Login successful" });
    } else {
      return res.status(401).json({ message: "Wrong login credentials" });
    }
  } catch (error) {
    console.error("Error:", error);
    return res.status(500).json({ message: "Internal server error" });
  }
});


capstone_proj.listen(process.env.backendport, () => {
    console.log("Backend listening on " + process.env.backendport)
})

//getdata(); 

The error that I am getting:

Error: ValidationException: The provided key element does not match the schema
    at throwDefaultError (D:Coding WorkspacesCapstonebackend-AWSnode_modules@smithysmithy-clientdist-cjsdefault-error-handler.js:8:22)
    at D:Coding WorkspacesCapstonebackend-AWSnode_modules@smithysmithy-clientdist-cjsdefault-error-handler.js:18:39
    at de_GetItemCommandError (D:Coding WorkspacesCapstonebackend-AWSnode_modules@aws-sdkclient-dynamodbdist-cjsprotocolsAws_json1_0.js:1554:20)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async D:Coding WorkspacesCapstonebackend-AWSnode_modules@smithymiddleware-serdedist-cjsdeserializerMiddleware.js:7:24
    at async D:Coding WorkspacesCapstonebackend-AWSnode_modules@aws-sdklib-dynamodbdist-cjsbaseCommandDynamoDBDocumentClientCommand.js:26:34
    at async D:Coding WorkspacesCapstonebackend-AWSnode_modules@aws-sdkmiddleware-signingdist-cjsawsAuthMiddleware.js:14:20
    at async D:Coding WorkspacesCapstonebackend-AWSnode_modules@smithymiddleware-retrydist-cjsretryMiddleware.js:27:46
    at async D:Coding WorkspacesCapstonebackend-AWSnode_modules@aws-sdkmiddleware-loggerdist-cjsloggerMiddleware.js:7:26
    at async file:///D:/Coding%20Workspaces/Capstone/backend-AWS/index.js:46:18 {
  '$fault': 'client',
  '$metadata': {
    httpStatusCode: 400,
    requestId: 'N9OAQBOPOSM5NV38FE5FNCLMQ3VV4KQNSO5AEMVJF66Q9ASUAAJG',
    extendedRequestId: undefined,
    cfId: undefined,
    attempts: 1,
    totalRetryDelay: 0
  },
  __type: 'com.amazon.coral.validate#ValidationException'
}