template.yml

AWSTemplateFormatVersion: "2010-09-09"
Description: Example of how to auto scale down resources to safe cost
Transform: AWS::Serverless-2016-10-31
Parameters:
  ScaleDownOffHours:
    Type: String
    Default: "false"

Conditions:
  ConfigureScaleDownOffHours: !Equals [ "true", !Ref ScaleDownOffHours ]

Resources:
  DatabaseSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: DB Security Group

  DatabaseCluster:
    Type: AWS::RDS::DBCluster
    Properties:
      Engine: aurora-postgresql
      EngineVersion: "14"
      MasterUsername: postgres
      ManageMasterUserPassword: true

  Database:
    Type: AWS::RDS::DBInstance
    Properties:
      Engine:  aurora-postgresql
      DBInstanceClass: "db.t4g.medium"
      DBClusterIdentifier: !Ref DatabaseCluster
      PubliclyAccessible: 'true'

  ScaleDownOffHoursStateMachine:
    Condition: ConfigureScaleDownOffHours
    Type: AWS::Serverless::StateMachine
    Properties:
      Events:
        ScaleDown:
          Type: ScheduleV2
          Properties:
            ScheduleExpressionTimezone: America/Chicago
            ScheduleExpression: "cron(0 17 * * ? *)"
        ScaleUp:
          Type: EventBridgeRule
          Properties:
            Pattern:
              source: [ "aws.cloudformation" ]
              account: [ !Ref AWS::AccountId ]
              detail-type: [ "CloudFormation Stack Status Change" ]
              detail:
                stack-id: [ !Ref AWS::StackId ]
                status-details:
                  status: [ "UPDATE_IN_PROGRESS" ]
      Policies:
        - Version: '2012-10-17'
          Statement:
            - Effect: Allow
              Action:
                - rds:StopDBCluster
                - rds:StartDBCluster
              Resource:
                - !GetAtt DatabaseCluster.DBClusterArn
      Definition:
        StartAt: DetermineDirection
        States:
          DetermineDirection:
            Type: Choice
            Choices:
              - Variable: "$$.Execution.Input.source"
                StringEquals: aws.scheduler
                Next: ScaleDown
            Default: ScaleUp
          ScaleUp:
            Type: Task
            Resource: "arn:aws:states:::aws-sdk:rds:startDBCluster"
            Parameters:
              DbClusterIdentifier: !Ref DatabaseCluster
            End: true
          ScaleDown:
            Type: Task
            Resource: "arn:aws:states:::aws-sdk:rds:stopDBCluster"
            Parameters:
              DbClusterIdentifier: !Ref DatabaseCluster
            End: true