Serverless CQRS

This template demonstrates how to deploy a CQRS pattern on AWS Lambda using the Serverless Framework.

Motivation

Defining a consistent pattern of querying the data from a distributed system.

• The Read/Write model in distributed systems often has asymmetric structure due to the separation of concerns.
• Some queries in a distributed system may need to serve a complex and aggregated data model owned by multiple Microservices.
• Two methods of implementing the Read model:
  • The API composition pattern— Simpler approach, It works by making clients of the services that own the data responsible for invoking the services and combining the results.
  • The Command query responsibility segregation (CQRS) pattern—This is more powerful than the API composition pattern, but it’s also more complex. It maintains one or more view databases whose sole purpose is to support queries.
• This template aims at addressing the baseline complexity of setting up a CQRS pattern, with serverless compute mode (FaaS) on AWS Lambda and API Gateway implementations.
• Why Serverless ?
  • It enforces stateless and pure functions.
  • The cost of operation is low (invocation based).
  • Infrastructure management is less and capacity planning can be more elastic.
  • Better suited for event driven async communication.

Usage

Deployment

In order to deploy the example, you need to run the following command:

$ 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.zip file to S3 (711.23 KB)...
Serverless: Validating template...
Serverless: Updating Stack...
Serverless: Checking Stack update progress...
.................................
Serverless: Stack update finished...
Service Information
service: aws-node
stage: dev
region: us-east-1
stack: aws-node-dev
resources: 6
functions:
  api: aws-node-dev-hello
layers:
  None

Invocation

After successful deployment, you can invoke the deployed function by using the following command:

serverless invoke --function hello

Which should result in response similar to the following:

{
    "statusCode": 200,
    "body": "{\n  \"message\": \"Go Serverless v2.0! Your function executed successfully!\",\n  \"input\": {}\n}"
}

Local development

You can invoke your function locally by using the following command:

serverless invoke local --function hello

Which should result in response similar to the following:

{
    "statusCode": 200,
    "body": "{\n  \"message\": \"Go Serverless v2.0! Your function executed successfully!\",\n  \"input\": \"\"\n}"
}