While looking around for a frugal way to host a node app I came across Serverless architecture. Here follows a massive simplification of Serverless architecture from the perspective of a front-end developer. Essentially Serverless involves splitting out:

1. Server-side JS into individual functions (e.g. get-user), these are then run on a cloud service such as AWS Lambda. When run on Lambda, these functions exist as stateless containers, and are called on demand by the front-end (e.g. via a GET endpoint of /user/{id}).
2. Front-end HTML, JS and CSS etc to be uploaded to a static host, such as AWS S3

For data storage a cloud solution such as AWS DynamoDB or MongoDB Atlas can be used.

Benefits

1. It’s cheap. As your functions on Lambda are called on demand, you are only using AWS’s computing power for a minute amount of time - compared to having an EC2 instance on all the time. Currently the Lambda free-tier is 1 million requests a month!
2. Scaling an app is much cheaper as a result of benefit #1
3. Suited for easily plugging-in BaaS (back-end as a service - e.g. Firebase) options for reduced development time.

Drawbacks

1. It’s a bit of a pain to split out functions and deploy / test them separately on Lambda (see below for example)
2. Reliant on 3rd-party services - security, API upgrade issues etc.

A simple Serverless app

To test it out, let’s build a simple app that will store info about Australian states in a database and return current data from said database. Deploying Serverless apps is made infinity easier by the Serverless npm package, which we will be using. The source for this example can be found at https://github.com/jonjhiggins/serverless-test.

Setup AWS and connect to it

1. Install Serverless npm i serverless -g
2. Register and log-in to AWS
3. Create an IAM user called serverless-admin with AdministratorAccess permissions (more info)
4. Create an AWS profile on your machine to connect to your AWS instance serverless config credentials --provider aws --key AKIAIOSFODNN7EXAMPLE --secret wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY (more info)

Build the project

1. mkdir serverless-test && cd $_
2. Create file serverless.yml - this contains all the configuration the Serverless npm package needs to deploy to AWS.
3. Add the following content to serverless.yml:

service: serverless-test

frameworkVersion: ">=1.1.0 <2.0.0"

provider:
  name: aws
  runtime: nodejs4.3
  environment:
    DYNAMODB_TABLE: ${self:service}-${opt:stage, self:provider.stage}
  iamRoleStatements:
    - Effect: Allow
      Action:
        - dynamodb:Scan
        - dynamodb:PutItem
      Resource: "arn:aws:dynamodb:${opt:region, self:provider.region}:*:table/${self:provider.environment.DYNAMODB_TABLE}"

functions:
  create:
    handler: states/create.create
    events:
      - http:
          path: states
          method: post
          cors: true

  list:
    handler: states/list.list
    events:
      - http:
          path: states
          method: get
          cors: true

resources:
  Resources:
    ServerlessTestTable:
      Type: "AWS::DynamoDB::Table"
      DeletionPolicy: Retain
      Properties:
        AttributeDefinitions:
          - AttributeName: id
            AttributeType: S
        KeySchema:
          - AttributeName: id
            KeyType: HASH
        ProvisionedThroughput:
          ReadCapacityUnits: 1
          WriteCapacityUnits: 1
        TableName: ${self:provider.environment.DYNAMODB_TABLE}

This configuration make look complicated, but there’s not too much too it:

• In provider we’re hooking up to the DynamoDB table that will be our database, iamRoleStatements allow specific actions on the table that we’ll reference in our Lambda functions.
• In functions we list out the Lambda functions, handler references their path in the project (e.g. ‘states/create.js’ has a function “create”). In events we create the HTTP endpoint (e.g. ‘/states’).
• In resources we create or reference DynamoDB table “ServerlessTestTable” which will store our data.

5. Create states/create.js and states/list.js. These will contain the functions that create and list states respectively.
6. Add the following content to states/create.js:

const AWS = require("aws-sdk"); // eslint-disable-line import/no-extraneous-dependencies

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

module.exports.create = (event, context, callback) => {
  const uuid = Math.floor(Math.random() * 100000000).toString();
  const data = JSON.parse(event.body);
  if (
    typeof data.state !== "string" ||
    typeof data.slogan !== "string" ||
    typeof data.capital !== "string"
  ) {
    console.error("Validation Failed");
    callback(new Error("Couldn't create a new Australian state."));
    return;
  }

  const params = {
    TableName: process.env.DYNAMODB_TABLE,
    Item: {
      id: uuid,
      state: data.state,
      slogan: data.slogan,
      capital: data.capital,
    },
  };

  // write the state to the database
  dynamoDb.put(params, (error) => {
    // handle potential errors
    if (error) {
      console.error(error);
      callback(new Error("Couldn't create a new Australian state."));
      return;
    }

    // create a response
    const response = {
      statusCode: 200,
      body: JSON.stringify(params.Item),
    };
    callback(null, response);
  });
};

6. Add the following content to states/list.js:

const AWS = require("aws-sdk"); // eslint-disable-line import/no-extraneous-dependencies

const dynamoDb = new AWS.DynamoDB.DocumentClient();
const params = {
  TableName: process.env.DYNAMODB_TABLE,
};

module.exports.list = (event, context, callback) => {
  // fetch all states from the database
  dynamoDb.scan(params, (error, result) => {
    // handle potential errors
    if (error) {
      console.error(error);
      callback(new Error("Couldn't fetch the Australian states."));
      return;
    }

    // create a response
    const response = {
      statusCode: 200,
      body: JSON.stringify(result.Items),
    };
    callback(null, response);
  });
};

7. Deploy using serverless deploy, make a note of the endpoint URLs at the end
8. Add a state with a cURL request (replacing XXXXXXX with the ID within the endpoint URLs from previous step): curl -X POST https://XXXXXXX.execute-api.us-east-1.amazonaws.com/dev/states --data '{ "state": "South Australia", "slogan": "The Wine State", "capital": "Adelaide" }'
9. View the states in the database with a cURL request: curl -X GET https://XXXXXXX.execute-api.us-east-1.amazonaws.com/dev/states

Going further

That simple example was adapted an the example project on Serverless examples, there’s loads more examples in the parent repo. In particular, the offline examples are useful for running Serverless locally for debugging. There’s no front-end for this example, but that could be created and hosted on S3.