How about using the Lambda function and not worrying too much about availability with guaranteed execution and direct access to DynamoDB?

The purpose of this article is to show you in a simple way how to create a serverless lambda function with direct access to DynamoDB.

I assume that you already have knowledge of JavaScript, AWS, Lambda concept and Serverless framework. Ok?

Let's start!

Let's create a simple function that performs a query on the DynamoDB database. See the example code below:

index.js

"use strict"

const AWS = require('aws-sdk');
AWS.config.update({region: 'us-east-1'});
const ddb = new AWS.DynamoDB({apiVersion: '2012-08-10'});

const params = {
  ExpressionAttributeValues: {    
    ':id': '67554837_xxx',
  },
  KeyConditionExpression: 'Id = :id',
  ProjectionExpression: 'Id, createdAt',
  TableName: 'Table_Name',
};

exports.handle = async function(event, context, callback) {
  try {  
    const dyn = await ddb.query(params, (err, data) => {
      if (err) {
        console.error('Error', JSON.stringify(err, null, 2));
      } else {
        console.log('Success');
        data.Items.forEach((item) => {
          console.log('item:', item);
        });        
      }
    }).promise();

    return dyn;
  } catch (e) {
    console.log(e);
    return e
  } 
}

Let's go to the serverless configuration now.

In the serverless.yml file we will configure the following:

What's inside the custom key are variables that are declared. It's a place to declare different types of variables.

Serverless has plugins that are community created extensions to what it can do.

In this case we are using some plugins, and specifically the serverless-domain-manager plugin requires some variables declared inside the custom to know how to make the correct DNS annotations (for friendly DNS terms to connect to the API Gateway it creates).

To access other AWS services, another plugin is used, which is serverless-iam-roles-per-function. Which allows Serverless to interpret these settings correctly:

See full serverless.yml file below:

service: lambda-dynamodb
frameworkVersion: '2'

package:
  individually: true
  patterns:
    - '!node_modules/**'
    - '!.env*'
    - '!package-lock.json'
    - '!package.json'

provider:
  name: aws
  runtime: nodejs12.x
  lambdaHashingVersion: 20201221
  httpApi:
    cors: true

plugins:
  - serverless-domain-manager
  - serverless-dotenv-plugin
  - serverless-latest-layer-version
  - serverless-iam-roles-per-function

custom:  
  customDomain:
    http:
      domainName: '${self:custom.domainNames.${self:custom.deploymentStage}}'
      certificateName: domain.com
      basePath: ''
      createRoute53Record: true
      endpointType: 'regional'
      securityPolicy: tls_1_2
  deploymentStage: ${opt:stage, 'staging'}
  domainNames:
    staging: staging.domain.com
    main: prod.domain.com

functions:
  get-dynamodb:    
    name: get-dynamodb
    handler: index.handle    
    iamRoleStatementsInherit: true
    iamRoleStatements:
      - Effect: "Allow"        
        Action:
          - dynamodb:Query
          - dynamodb:Scan
          - dynamodb:GetItem       
        Resource: "arn:aws:dynamodb:us-east-1:897362587641:table/Table_Name"
    events:
      - httpApi:
          path: /dynamodb
          method: get

Deploy your function

There are some efficient ways to deploy the function. Via command line or using AWS Serverless CI/CD to automate the deployment process in a production environment, for example.

Command line

$ serverless deploy

For more details and other command execution options, take a look at the serverless doc: https://www.serverless.com/framework/docs/providers/aws/cli-reference/deploy

For a production environment, look at this AWS doc
https://aws.amazon.com/quickstart/architecture/serverless-cicd-for-enterprise/


Follow our open source projects on Github! https://github.com/Cloudoki