Workaround of using Serverless Aurora V2 with the AWS CDK

infra-stack.ts

// https://github.com/aws/aws-cdk/issues/20197
enum ServerlessInstanceType {
  SERVERLESS = "serverless",
}

type CustomInstanceType = ServerlessInstanceType | ec2.InstanceType;

const CustomInstanceType = {
  ...ServerlessInstanceType,
  ...ec2.InstanceType,
};

const dbClusterInstanceCount: number = 1;

const vpc: ec2.Vpc = new ec2.Vpc(this, "InfraVPC", {
  maxAzs: 2,
  natGateways: 1,
  vpcName: "infra-vpc",
  subnetConfiguration: [
    {
      cidrMask: 24,
      name: "private-subnet",
      subnetType: ec2.SubnetType.PRIVATE_ISOLATED,
    },
    {
      cidrMask: 24,
      name: "public-subnet",
      subnetType: ec2.SubnetType.PUBLIC,
    },
  ],
});

const dbCluster: rds.DatabaseCluster = new rds.DatabaseCluster(
  this,
  "ServerlessAuroraDbCluster",
  {
    engine: rds.DatabaseClusterEngine.auroraPostgres({
      version: rds.AuroraPostgresEngineVersion.VER_13_7,
    }),
    clusterIdentifier: "ServerlessAuroraDbCluster",
    removalPolicy: RemovalPolicy.DESTROY,
    defaultDatabaseName: "orders",
    instances: dbClusterInstanceCount,
    instanceProps: {
      vpc: vpc,
      deleteAutomatedBackups: true,
      instanceType:
        CustomInstanceType.SERVERLESS as unknown as ec2.InstanceType,
      autoMinorVersionUpgrade: false,
      publiclyAccessible: false,
      vpcSubnets: {
        subnetType: ec2.SubnetType.PRIVATE_ISOLATED,
      },
    },
    backup: {
      retention: Duration.days(1),
      preferredWindow: "08:00-09:00",
    },
    port: 5432,
    cloudwatchLogsExports: ["postgresql"],
    cloudwatchLogsRetention: logs.RetentionDays.ONE_DAY,
    storageEncrypted: true,
  }
);

const serverlessV2ScalingConfiguration = {
  MinCapacity: 0.5,
  MaxCapacity: 1,
};

const dbConnectionGroup: ec2.SecurityGroup = new ec2.SecurityGroup(
  this,
  "RdsProxyDBConnection",
  {
    vpc,
    securityGroupName: "rds-proxy-sg",
  }
);

dbConnectionGroup.addIngressRule(
  dbConnectionGroup,
  ec2.Port.tcp(5432),
  "allow db connection"
);

const cfnDbCluster: rds.CfnDBCluster = dbCluster.node
  .defaultChild as rds.CfnDBCluster;
const dbScalingConfigureTarget = dbScalingConfigure.node.findChild(
  "Resource"
).node.defaultChild as CfnResource;

cfnDbCluster.addPropertyOverride("EngineMode", "provisioned");
dbScalingConfigure.node.addDependency(cfnDbCluster);

for (let i = 1; i <= dbClusterInstanceCount; i++) {
  (
    dbCluster.node.findChild(`Instance${i}`) as rds.CfnDBInstance
  ).addDependsOn(dbScalingConfigureTarget);
}