5. Dependency Graphs, Provisioners, and Safe Replacement

Terraform builds a dependency graph from references and explicit `depends_on`. It can then create independent resources in parallel. Prefer resource arguments and provider resources over provisioners because provisioners are harder to observe, retry, and reproduce.

`create_before_destroy` can reduce downtime when a replacement resource can coexist with the old one. It is not universally safe: names, quotas, uniqueness constraints, and stateful resources may prevent overlap.