Which Terraform collection type is best for storing key/value pairs?

The best collection type for storing key/value pairs in Terraform is a Map. A Map is an unordered collection composed of unique keys that are associated with values. This structure allows for easy retrieval and management of data based on the specified keys, making it suitable for various configuration scenarios.

Maps are particularly advantageous when you want to associate specific configurations or settings with identifiable keys, as they provide greater readability and organization. For example, in scenarios where you are defining resource attributes or passing configuration variables, using a Map can help you define those relationships clearly.

On the other hand, Lists, Sets, and Arrays do not support key/value data structures. Lists are ordered collections that allow duplicate values but do not associate values with unique keys. Sets, while also unordered and unique, only store values without a corresponding key, which limits their functionality for storing pairs. Arrays are not a distinct collection type in Terraform terminology and typically refer to ordered lists in programming, again without key associations. Thus, a Map is the optimal choice for managing key/value pairs in Terraform.