Well Formed AWS Lambda for DynamoDB

Well Formed AWS Lambda for DynamoDB

// Set up AWS client
var AWS = require('aws-sdk');
var dynamodb = new AWS.DynamoDB();

// TODO update AWS configuration to set region
AWS.config.update({region : 'us-east-1'});

exports.handler = function(event, context) {
    // Keep tracxk of how many requests are in flight
    var inflightRequests = 0;
    
    event.Records.forEach(function(record) {
        console.log('DynamoDB Record: %j', record.dynamodb);
        // Get the new image of the DynamoDB Streams record
        var newItemImage = record.dynamodb.NewImage;
        
        // Set the appropriate parameters for UpdateItem
        // Refer to the ADD operation in the UpdateItem API for UpdateExpression
        // http://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_UpdateItem.html
        // Adds the specified value to the item, if attribute does not exist, set the attribute
        var updateItemParams = {
            TableName: "GameScoresByUser",
            Key: {
                Username: newItemImage.Username
            },
            UpdateExpression: 'ADD Score :attrValue',
            ExpressionAttributeValues: {':attrValue' : newItemImage.Score }
        }
        
        // Make a callback function to execute once UpdateItem request completes
        // It may be helpful to refer to the updateItem method for the Javascript SDK
        // http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/DynamoDB.html#updateItem-property 
        var updateItemCallback = function(err, data) {
        if (err) {
            // log errors
            console.log(err, err.stack);
            } else {
                // check if all requests are finished, if so, end the function
                inflightRequests--;
                if (inflightRequests === 0) {
                    context.succeed("Successfully processed " + event.Records.length + " records.");
                }
            }
        };
        
        // TODO send UpdateItem request to DynamoDB
        dynamodb.updateItem(updateItemParams, updateItemCallback);
        // TODO increase count for number of requests in flight
        inflightRequests++;
    });
    
    // If there are no more requests pending, end the function
    if (inflightRequests === 0) {
        context.succeed("Successfully processed " + event.Records.length + " records.");
    }
}; 

When I try this code I get validation errors.
[MultipleValidationErrors: There were 2 validation errors:

• InvalidParameterType: Expected params.Key['Username'] to be a structure
• InvalidParameterType: Expected params.ExpressionAttributeValues[':attrValue'] to be a structure]

Using the DocumentClient seems to fix it:

var dynamodb = new AWS.DynamoDB.DocumentClient();