CloudFormation outputs

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Goal

After this page you will understand how to export values from one CloudFormation/CDK stack and import them into another, enabling cross-stack references.

Prerequisites

• IaC with CDK — you have a deployed CDK stack.

Why cross-stack references

As your infrastructure grows, you will split resources across multiple stacks:

Stack	Resources
DatabaseStack	DynamoDB tables
AuthStack	Cognito User Pool
ApiStack	Lambda, API Gateway, authorizer
FrontendStack	S3 bucket, CloudFront

Stack A (e.g. DatabaseStack) exports values (table name, ARN). Stack B (e.g. ApiStack) imports them. This keeps each stack focused and independently deployable.

Export an output in CDK

In your CDK stack, use CfnOutput with exportName:

import { CfnOutput } from "aws-cdk-lib";

// Inside the stack constructor:
new CfnOutput(this, "ItemsTableName", {
  value: table.tableName,
  exportName: "ItemsTableName",
});

new CfnOutput(this, "ItemsTableArn", {
  value: table.tableArn,
  exportName: "ItemsTableArn",
});

When you deploy, CloudFormation registers these as exports visible to other stacks in the same account and region.

Import in another stack

import { Fn } from "aws-cdk-lib";

// Inside a different stack:
const tableName = Fn.importValue("ItemsTableName");
const tableArn = Fn.importValue("ItemsTableArn");

The import creates a cross-stack reference. The exporting stack cannot be deleted as long as any importing stack references it.

View exports via CLI

# List all exported outputs in the region.
aws cloudformation list-exports --region us-east-1

Output example:

{
  "Exports": [
    {
      "Name": "ItemsTableName",
      "Value": "items",
      "ExportingStackId": "arn:aws:cloudformation:us-east-1:123456789012:stack/ItemsCdkStack/..."
    },
    {
      "Name": "ItemsTableArn",
      "Value": "arn:aws:dynamodb:us-east-1:123456789012:table/items",
      "ExportingStackId": "arn:aws:cloudformation:us-east-1:123456789012:stack/ItemsCdkStack/..."
    }
  ]
}

CloudFormation outputs vs SSM Parameter Store

Approach	Best for
Fn::ImportValue / CfnOutput	Cross-stack references within one account/region
SSM Parameter Store	Cross-account, cross-region, or non-CloudFormated resources
Secrets Manager	Secrets (database passwords, API keys)

SSM Parameter Store example:

# Write a parameter.
aws ssm put-parameter --name /items-api/table-name --value items --type String

# Read it in CDK:
import { StringParameter } from "aws-cdk-lib/aws-ssm";
const tableName = StringParameter.fromStringParameterName(this, "TableName", "/items-api/table-name");

Checkpoint

Add a CfnOutput with exportName to your CDK stack, redeploy, and verify the export appears:

# PLACEHOLDER — use your own region.
aws cloudformation list-exports --region us-east-1 --query "Exports[?starts_with(Name, 'Items')]"

Expected: at least one export with Name starting with "Items" and the corresponding Value and ExportingStackId.

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