When an API endpoint updates in-memory state (e.g. cached credentials, config objects), that change only affects the worker process that handled the request. With multiple FastAPI workers, **use `WorkerSyncManager`** (`services/worker_sync/`) to propagate changes to all workers via Redis pub/sub instead of updating local state directly.
Most resources in this codebase are scoped to an organization. **Whenever you read or write an organization-scoped field, you must filter or validate by `organization_id`.** This is a tenant-isolation requirement, not a stylistic one — skipping the check lets a user in one org touch resources owned by another.
Concretely:
- **Reading** an org-scoped row by id: pass `organization_id=user.selected_organization_id` to the DB client (or query through an org-scoped helper). Never trust an id from the request body to imply ownership.
- **Writing** a foreign key that points at another org-scoped resource (e.g. attaching `inbound_workflow_id` to a phone number, setting `telephony_configuration_id` on a campaign): fetch the referenced row with the user's `organization_id` and reject with 404 if it doesn't belong. The FK constraint only proves the row exists — it doesn't prove the caller is allowed to reference it.
- **Listing** org-scoped resources: filter by `organization_id` at the query level, not in Python after the fact.
If a route's handler does not have access to an `organization_id` (e.g. webhook callbacks), derive it from the request payload and validate that derivation explicitly — don't assume.
