Terraform map for expressions decide more than formatting. They define identity.
A list changes order. A map changes meaning.
When you build a map with a for expression, you are assigning keys that Terraform uses as resource addresses. That key becomes part of state. That means a simple rename is not a rename. It is a destroy and recreate event.
This lesson breaks down how map for expressions work, how filtering affects key presence, and how transformed maps feed directly into for_each. The goal is not syntax. The goal is control over infrastructure lifecycle.
If you treat keys like labels, you will eventually break something.