Worked on the ssc-sp/datahub-portal repository to deliver tenant-aware user existence validation during login, addressing the need for accurate cross-tenant checks and reducing login friction. Designed and implemented the IUserInformationService interface and its C#-based implementations to enable querying user existence by email across tenants. Updated the backend login flow to gracefully handle scenarios where a user is registered in the tenant but not yet present in the portal, improving both accuracy and user experience. Focused on backend development and API integration, the work enhanced authentication logic to enforce correct tenant scoping and provided a more robust, maintainable login process.