templated_vars_snippet.yaml

---
...
stages:
- stage:
  displayName: 'Terraform Plan'
  jobs:
  - job: TFPlan
    variables: # <--Variables are now scoped to this job and all steps within it
      - template: vars/dev_vars.yml
    steps:
      - task: Cache@2
        displayName: 'Register TF cache'
        inputs:
          key: terraform | $(Agent.OS) | "$(Build.BuildNumber)" | $(Build.SourceVersion) | $(tfComponent) | "$(tfVarFileName)"
          path: $(tfExecutionDir)
 ...