DynamicLambdaConfig.js

var aws = require('aws-sdk');
var fs = require("fs");
var Promise = require("es6-promise").Promise;

/**
 * Load Configuration from local file or from DynamoDB.
 */
var loadConfig = function(){
	return new Promise( function(resolve, reject) {
		try {
			// If we have it locally.
			if ( fs.existsSync('/tmp/config.json') ){
				var c = JSON.parse(fs.readFileSync( '/tmp/config.json' ));
				resolve(c);
			}
		} catch(  e ){
			// Send Error Message, but load from dynamic
		  console.log( e.message );
		}

    // Specific to my work
		var params = {
			TableName: 'myLambdaConfig',
			Key: { 'service': 'photos' }
		};
		var dynamoDb = new aws.DynamoDB.DocumentClient({region:'us-east-1',version:'latest'});
		dynamoDb.get(params, function(err, data) {
			if ( err ) { 
				reject(err);
			}
			if ( data['Item'] && data['Item']['config'] ){
				fs.writeFileSync( '/tmp/config.json', JSON.stringify(data['Item']['config']) );
				resolve(data['Item']['config']);
			} else {
				reject("Empty Config.");
			}
		});
	});
}

loadConfig().then(
	function( config ) { console.log( config ); },
	function( error ) { console.log( "Failed to load config."  + error ); }
);