How to do it...

1. Create the project from the following template:

$ sls create --template-url https://github.com/danteinc/js-cloud-native-cookbook/tree/master/ch2/micro-event-store --path cncb-micro-event-store

2. Navigate to the cncb-micro-event-store directory with cd cncb-micro-event-store.
3. Review the file named serverless.yml with the following content:

service: cncb-micro-event-store

provider:
  name: aws
  runtime: nodejs8.10
  iamRoleStatements:
    - Effect: Allow
      Action:
        - dynamodb:PutItem
        - dynamodb:Query
      Resource:
        Fn::GetAtt: [ Table, Arn ]
  environment:
    TABLE_NAME:
      Ref: Table

functions:
  listener:
    handler: handler.listener
    events:
      - stream:
          type: kinesis
          ...
  trigger:
    handler: handler.trigger
    events:
      - stream:
          type: dynamodb
          arn:
            Fn::GetAtt: [ Table, StreamArn ]
          batchSize: 100
          startingPosition: TRIM_HORIZON

resources:
  Resources:
    Table:
      Type: AWS::DynamoDB::Table
      Properties:
        TableName: ${opt:stage}-${self:service}-events
        AttributeDefinitions:
          ...
        KeySchema:
          - AttributeName: partitionKey
            KeyType: HASH
          - AttributeName: eventId
            KeyType: RANGE
        ...
        StreamSpecification:
          StreamViewType: NEW_AND_OLD_IMAGES

4. Review the file named handler.js with the following content:

module.exports.listener = (event, context, cb) => {
  _(event.Records)
    .map(recordToEvent)
    .filter(byType)
    .flatMap(put)
    .collect()
    .toCallback(cb);
};

...
const byType = event => event.type.matches(/thing-.+/);

const put = event => {
  const params = {
    TableName: process.env.TABLE_NAME,
    Item: {
      partitionKey: event.partitionKey,
      eventId: event.id,
      event: event,
    }
  };

  const db = new aws.DynamoDB.DocumentClient();
  return _(db.put(params).promise());
};

module.exports.trigger = (event, context, cb) => {
  _(event.Records)
    .flatMap(getMicroEventStore)
    .tap(events => console.log('events: %j', events))
    .collect().toCallback(cb);
};

const getMicroEventStore = (record) => {
  const params = {
    TableName: process.env.TABLE_NAME,
    KeyConditionExpression: '#partitionKey = :partitionKey',
    ExpressionAttributeNames: {
      '#partitionKey': 'partitionKey'
    },
    ExpressionAttributeValues: {
      ':partitionKey': record.dynamodb.Keys.partitionKey.S
    }
  };

  const db = new aws.DynamoDB.DocumentClient();
  return _(db.query(params).promise());
}

5. Install the dependencies with npm install.
6. Run the tests with npm test -- -s $MY_STAGE.
   
7. Review the contents generated in the .serverless directory.
8. Deploy the stack:

$ npm run dp:lcl -- -s $MY_STAGE

> cncb-micro-event-store@1.0.0 dp:lcl <path-to-your-workspace>/cncb-micro-event-store
> sls deploy -v -r us-east-1 "-s" "john"

Serverless: Packaging service...
...
Serverless: Stack update finished...
...
functions:
  listener: cncb-micro-event-store-john-listener
  trigger: cncb-micro-event-store-john-trigger
...

9. Review the stack, functions, and table in the AWS Console.
10. Publish an event from a separate Terminal with the following commands:

$ cd <path-to-your-workspace>/cncb-event-stream
$ sls invoke -r us-east-1 -f publish -s $MY_STAGE -d '{"type":"thing-updated","partitionKey":"11111111-1111-1111-1111-111111111111","thing":{"new":{"name":"thing one","id":"11111111-1111-1111-1111-111111111111"}}}'

{
    "ShardId": "shardId-000000000000",
    "SequenceNumber": "49583553996455686705785668952922460091805481438885707778"
}

11. Take a look at the logs for the listener function:

$ sls logs -f listener -r us-east-1 -s $MY_STAGE

START ...
2018-04-18 01:18:55... {"type":"thing-updated","partitionKey":"11111111-1111-1111-1111-111111111111","thing":{"new":{"name":"thing one","id":"11111111-1111-1111-1111-111111111111"}},"id":"fcc03460-42c7-11e8-8756-f75e650b2731","timestamp":1524028734118,"tags":{"region":"us-east-1"}}
2018-04-18 01:18:55.394 (-04:00)    b42aaa92-8a9a-418d-8e22-ecc54e9966f6    params: {"TableName":"john-cncb-micro-event-store-events","Item":{"partitionKey":"11111111-1111-1111-1111-111111111111","eventId":"fcc03460-42c7-11e8-8756-f75e650b2731","event":{"type":"thing-updated","partitionKey":"11111111-1111-1111-1111-111111111111","thing":{"new":{"name":"thing one","id":"11111111-1111-1111-1111-111111111111"}},"id":"fcc03460-42c7-11e8-8756-f75e650b2731","timestamp":1524028734118,"tags":{"region":"us-east-1"}}}}
END ...
REPORT ... Duration: 149.24 ms    Billed Duration: 200 ms ... Max Memory Used: 35 MB    

12. Take a look at the logs for the trigger function: 

$ sls logs -f trigger -r us-east-1 -s $MY_STAGE

START ...
2018-04-18 01:18:56 ... event: {"Records":[{"eventID":"b8dbee2d9f49ee05609a7e930ac204e7","eventName":"INSERT",...,"Keys":{"eventId":{"S":"fcc03460-42c7-11e8-8756-f75e650b2731"},"partitionKey":{"S":"11111111-1111-1111-1111-111111111111"}},...}]}
2018-04-18 01:18:56 ... params: {"TableName":"john-cncb-micro-event-store-events",...,"ExpressionAttributeValues":{":partitionKey":"11111111-1111-1111-1111-111111111111"}}
2018-04-18 01:18:56 ... events: {"Items":[{"eventId":"2a1f5290-42c0-11e8-a06b-33908b837f8c","partitionKey":"11111111-1111-1111-1111-111111111111","event":{"id":"2a1f5290-42c0-11e8-a06b-33908b837f8c","type":"thing-submitted","partitionKey":"11111111-1111-1111-1111-111111111111","thing":{"name":"thing one","kind":"other","id":"11111111-1111-1111-1111-111111111111"},"timestamp":1524025374265,"tags":{"region":"us-east-1","kind":"other"}}},{"eventId":"fcc03460-42c7-11e8-8756-f75e650b2731","partitionKey":"11111111-1111-1111-1111-111111111111","event":{"id":"fcc03460-42c7-11e8-8756-f75e650b2731","type":"thing-updated","partitionKey":"11111111-1111-1111-1111-111111111111","thing":{"new":{"name":"thing one","id":"11111111-1111-1111-1111-111111111111"}},"timestamp":1524028734118,"tags":{"region":"us-east-1"}}}],"Count":2,"ScannedCount":2}
END ...
REPORT ... Duration: 70.88 ms    Billed Duration: 100 ms     Memory Size: 1024 MB    Max Memory Used: 42 MB    

13. Remove the stack once you have finished with npm run rm:lcl -- -s $MY_STAGE.