plan vs apply
also: dry-run, preview, two-phase commit
A two-step operational pattern where a system shows you what changes it will make (plan) before actually making them (apply), allowing review and approval first.
Plan vs Apply is a workflow design pattern that separates the preview phase from the execution phase. The plan step shows exactly what changes will occur without making them; the apply step then executes those approved changes.
This pattern is most common in Infrastructure-as-Code (IaC) tools like Terraform. Running terraform plan displays all resource creations, modifications, and deletions in a diff format, letting you review before committing. Only after approval do you run terraform apply to execute the changes.
The pattern prevents accidental destructive changes—you can catch mistakes, security issues, or unintended modifications during the plan review stage rather than discovering them after infrastructure is already altered.