This template demonstrates how to develop and deploy a simple Node Express API service, backed by DynamoDB database, running on AWS Lambda using the traditional Serverless Framework.

This template configures a single function, api, which is responsible for handling all incoming requests thanks to the httpApi event. To learn more about httpApi event configuration options, please refer to httpApi event docs. As the event is configured in a way to accept all incoming requests, express framework is responsible for routing and handling requests internally. Implementation takes advantage of serverless-http package, which allows you to wrap existing express applications. To learn more about serverless-http, please refer to corresponding GitHub repository. Additionally, it also handles provisioning of a DynamoDB database that is used for storing data about users. The express application exposes two endpoints, POST /users and GET /user/{userId}, which allow to create and retrieve users.

Install dependencies with:

npm install

and then deploy with:

serverless deploy

After running deploy, you should see output similar to:

Serverless: Packaging service...
Serverless: Excluding development dependencies...
Serverless: Creating Stack...
Serverless: Checking Stack create progress...
........
Serverless: Stack create finished...
Serverless: Uploading CloudFormation file to S3...
Serverless: Uploading artifacts...
Serverless: Uploading service aws-node-express-dynamodb-api.zip file to S3 (718.53 KB)...
Serverless: Validating template...
Serverless: Updating Stack...
Serverless: Checking Stack update progress...
....................................
Serverless: Stack update finished...
Service Information
service: aws-node-express-dynamodb-api
stage: dev
region: us-east-1
stack: aws-node-express-dynamodb-api-dev
resources: 13
api keys:
  None
endpoints:
  ANY - https://xxxxxxx.execute-api.us-east-1.amazonaws.com/
functions:
  api: aws-node-express-dynamodb-api-dev-api
layers:
  None

Note: In current form, after deployment, your API is public and can be invoked by anyone. For production deployments, you might want to configure an authorizer. For details on how to do that, refer to httpApi event docs. Additionally, in current configuration, the DynamoDB table will be removed when running serverless remove. To retain the DynamoDB table even after removal of the stack, add DeletionPolicy: Retain to its resource definition.

After successful deployment, you can create a new user by calling the corresponding endpoint:

curl --request POST 'https://xxxxxx.execute-api.us-east-1.amazonaws.com/users' --header 'Content-Type: application/json' --data-raw '{"name": "John", "userId": "someUserId"}'

Which should result in the following response:

{"userId":"someUserId","name":"John"}

You can later retrieve the user by userId by calling the following endpoint:

curl https://xxxxxxx.execute-api.us-east-1.amazonaws.com/users/someUserId

Which should result in the following response:

{"userId":"someUserId","name":"John"}

If you try to retrieve user that does not exist, you should receive the following response:

{"error":"Could not find user with provided \"userId\""}

It is also possible to emulate DynamoDB, API Gateway and Lambda locally using the serverless-dynamodb-local and serverless-offline plugins. In order to do that, run:

serverless plugin install -n serverless-dynamodb-local
serverless plugin install -n serverless-offline

It will add both plugins to devDependencies in package.json file as well as will add it to plugins in serverless.yml. Make sure that serverless-offline is listed as last plugin in plugins section:

plugins:
  - serverless-dynamodb-local
  - serverless-offline

You should also add the following config to custom section in serverless.yml:

custom:
  (...)
  dynamodb:
    start:
      migrate: true
    stages:
      - dev

Additionally, we need to reconfigure AWS.DynamoDB.DocumentClient to connect to our local instance of DynamoDB. We can take advantage of IS_OFFLINE environment variable set by serverless-offline plugin and replace:

const dynamoDbClient = new AWS.DynamoDB.DocumentClient();

with the following:

const dynamoDbClientParams = {};
if (process.env.IS_OFFLINE) {
  dynamoDbClientParams.region = 'localhost'
  dynamoDbClientParams.endpoint = 'https://localhost:8000'
}
const dynamoDbClient = new AWS.DynamoDB.DocumentClient(dynamoDbClientParams);

After that, running the following command with start both local API Gateway emulator as well as local instance of emulated DynamoDB:

serverless offline start

To learn more about the capabilities of serverless-offline and serverless-dynamodb-local, please refer to their corresponding GitHub repositories:

• https://github.com/dherault/serverless-offline
• https://github.com/99x/serverless-dynamodb-local