AWS DynamoDB update item command gets ValidationException: The provided key element does not match the schema

Question

Given the table with `user_id (partition key)` and `created_at (sort key)`:

```
{
  "user_id": {
    "S": "..."
  },
  "created_at": {
    "N": "...."
  },
  "bot_answer": {
    "S": "..."
  },
  "question": {
    "S": "..."
  }
}
```

My lambda receives the insert event from dynamodb:

```
{
    "Records": [
        {
            ....
            "eventName": "INSERT",
            ....
            "dynamodb": {
                ....
                "Keys": {
                    "user_id": {
                        "S": "user123"
                    },
                    "created_at": {
                        "N": "1681218896790"
                    }
                },
                "NewImage": {
                    "question": {
                        "S": "What is the capital of USA?"
                    },
                    "user_id": {
                        "S": "user123"
                    },
                    "created_at": {
                        "N": "1681218896790"
                    },
                    "bot_answer": {
                        "S": ""
                    }
                },
                .....
                "StreamViewType": "NEW_AND_OLD_IMAGES"
            },
            ......
        }
    ]
}

```

I try to update an item with the command (from execution logs):

```
{
  TableName: 'chat_messages_tbl',
  Key: { 
   user_id: { S: 'user123' }, 
   created_at: { N: '1681218896790' } 
  },
  UpdateExpression: 'SET bot_answer = :bot_answer',
  ExpressionAttributeValues: { ':bot_answer': { S: 'Hello from bot!' } },
  ReturnValues: 'UPDATED_NEW'
}

```

But I get the `ValidationException: The provided key element does not match the schema`

```
// sample code from lambda (nodejs)

const dynamoDB = DynamoDBDocumentClient.from(dynamoDBClient)
const result = await dynamoDB.send(new UpdateCommand({
  TableName: 'chat_messages_tbl',
  Key: { 
   user_id: { S: 'user123' }, 
   created_at: { N: '1681218896790' } 
  },
  UpdateExpression: 'SET bot_answer = :bot_answer',
  ExpressionAttributeValues: { ':bot_answer': { S: 'Hello from bot!' } },
  ReturnValues: 'UPDATED_NEW'
}))
```

**NOTE** since the `created_at` is a `number`, I also **tried to send it in the update command without single quotes**:

```
created_at: { N: 1681218896790 }  // instead of { N : '1681218896790' } 
```

Thanks, F.

Fabio · Accepted Answer

Looks like you must pass native JS types:

```
Key: { 
    user_id: 'user123',  // No need to wrap in { S: '...' }
    created_at: 1681218896790  //  No need to wrap in  { N: '...' }
  },
```

Also, there is a lib to convert json to dynamodb types and back:

```
import {unmarshall, marshall} from '@aws-sdk/util-dynamodb'
```

Leeroy Hannigan · Answer

Here you are using the `DocumentClient` which accepts native JSON data:

`const dynamoDB = DynamoDBDocumentClient.from(dynamoDBClient)`

If you want to continue using DynamoDB JSON you can use the low level client which you have also created:

```js
// remove this client creation
// const dynamoDB = DynamoDBDocumentClient.from(dynamoDBClient)

// change the client to use the low level client you have created: dynamoDBClient
const result = await dynamoDBClient.send(new UpdateCommand({
  TableName: 'chat_messages_tbl',
  Key: { 
   user_id: { S: 'user123' }, 
   created_at: { N: '1681218896790' } 
  },
  UpdateExpression: 'SET bot_answer = :bot_answer',
  ExpressionAttributeValues: { ':bot_answer': { S: 'Hello from bot!' } },
  ReturnValues: 'UPDATED_NEW'
}))
```

Or if you want to use native JSON do the following:

```js
const dynamoDB = DynamoDBDocumentClient.from(dynamoDBClient)
const result = await dynamoDB.send(new UpdateCommand({
  TableName: 'chat_messages_tbl',
  Key: { 
   user_id: 'user123' , 
   created_at:  '1681218896790' 
  },
  UpdateExpression: 'SET bot_answer = :bot_answer',
  ExpressionAttributeValues: { ':bot_answer': 'Hello from bot!' },
  ReturnValues: 'UPDATED_NEW'
}))
```

If you want more information on the differences on clients, check out this blog post:
https://aws.amazon.com/blogs/database/exploring-amazon-dynamodb-sdk-clients/

AWS DynamoDB update item command gets ValidationException: The provided key element does not match the schema

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