Transport network operators support diverse services for multiple tenants. Wavelength division multiplexing (WDM) and space division multiplexing (SDM) enable optical virtual networks by using spatial channels and virtualized devices on top of the optical transport network infrastructure. Integrating network function virtualization (NFV) and software-defined networking (SDN) allows dynamic control of these networks in either the cloud or transport domain. This article presents microsegmentation of a microservice-based transport control plane to design an orchestration platform supporting multitenancy with security isolation across cloud and transport networks. The proposed architecture enables not only horizontal scaling through microservices but also vertical isolation through microsegmentation, and it allows controller virtualization in a cloud-native environment. The microsegmentation-based architecture makes it possible to guarantee a high level of operational independence among the SDN controllers for individual tenants and administrative autonomy of the optical virtual networks while preventing lateral interference between tenants.