SYMPTOM
Deployment 409 Conflict: resource exists with different immutable properties
CAUSE
Re-running a template 409s because a property that cannot change after creation differs (SKU family, Cosmos DB capabilities, some network settings), or a soft-deleted resource still holds the name.
CONFIRM IT
CONFIRM: `az deployment group show --name [d] -g [rg] --query properties.error.details` names the conflicting property; what-if shows the template trying to change it. For name-held: the resource appears in soft-deleted listings (e.g. `az keyvault list-deleted`).
FIX
FIX: immutable property: revert the template to the existing value, or recreate the resource deliberately (backup data first). Soft-deleted name: purge it (`az keyvault purge`) or wait out retention. Never script delete-then-create on stateful resources as conflict resolution.
VERIFY
VERIFY: what-if shows no changes, deployment reports Succeeded.