Adding telecom capabilities to a product looks straightforward in an API demo. A developer sends a request to activate an eSIM, reserve a phone number, assign a data plan or retrieve usage. The request returns successfully, and the team moves on. Production exposes the real problem. The carrier accepted the activation request, but the network state is still pending. A webhook arrives twice or out of order. An operation times out after the provider created the resource, so a retry creates a duplicate.
