Developed foundational sub-user management capabilities for the alphauslabs/blueapi repository, focusing on scalable multi-tenant access control. Designed and implemented new SubUser and SubUserRole message types using Protocol Buffers to define structured sub-user data, including identifiers, parent associations, metadata, and roles. Introduced a GetSubUserMetadata RPC in the iam.proto file, enabling programmatic retrieval of sub-user metadata through gRPC APIs. This work established a robust data model and API surface for sub-user governance, supporting future extensibility. The engineering approach emphasized clear data modeling and API design, leveraging protobuf and gRPC to ensure efficient, structured communication across distributed services without reported bugs.