Change Sets and Stack Updates

Updating production infrastructure is inherently risky. A single misconfigured property can cause downtime, data loss, or unexpected resource replacement. CloudFormation change sets address this risk by letting you preview exactly what will change before you apply an update. In this lesson, we will learn how to create, review, and execute change sets, and we will explore advanced update strategies.

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What is a Change Set?

A change set is a summary of the proposed changes to a stack. When you create a change set, CloudFormation compares your updated template with the current stack and generates a list of changes — without actually making any modifications.

Think of a change set as a "dry run" for your stack update.

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The Change Set Workflow

The workflow has three steps:

1. Create — submit your updated template and CloudFormation generates the change set
2. Review — examine the proposed changes to verify they are correct
3. Execute — apply the changes to the stack (or discard the change set)

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Creating a Change Set

Via the CLI