IT Infrastructure Engineer at kyivstar

We are looking for a senior, hands-on engineer to own and evolve our enterprise identity and messaging platforms in a hybrid Microsoft environment. About us  Kyivstar.Tech is a Ukrainian hybrid IT company and a resident of Diia.City. We are a subsidiary of Kyivstar, one of Ukraine's largest telecom operators.  Our mission is to change lives in Ukraine and around the world by creating technological solutions and products that unleash the potential of businesses and meet users' needs.  Over 600+ KS.Tech specialists work daily in various areas: mobile and web solutions, as well as design, development, support, and technical maintenance of high-performance systems and services.  We believe in innovations that truly bring quality changes and constantly challenge conventional approaches and solutions. Each of us is an adherent of entrepreneurial culture, which allows us never to stop, to evolve, and to create something new. What you will do • Lead the administration and evolution of Microsoft Active Directory in a complex enterprise environment. • Own Exchange and Exchange Hybrid (on-premises and Exchange Online), ensuring reliability, security, and seamless coexistence. • Design, operate, and maintain Public Key Infrastructure (PKI), including certificate lifecycle management. • Administer and develop Microsoft 365 / Entra ID identity services, roles, and access models. • Implement and support ADFS / SSO and federation scenarios for internal and external applications. • Ensure secure access control, authentication, and authorization across platforms. • Collaborate with network, platform, and application teams on identity-related integrations. • Drive continuous improvement of identity and messaging architectures and operational practices. Qualifications and experience needed • Strong hands-on expertise in Active Directory (architecture, trusts, GPO, troubleshooting). • Proven experience with Exchange (on-prem) and Exchange Hybrid. • Solid practical experience with PKI (Root/Issuing CAs, templates, CRL/OCSP). • Production experience with Microsoft 365 / Entra ID in hybrid environments. • Practical knowledge of ADFS / SSO, federation, and claims-based authentication. • Strong Windows Server background in enterprise environments. • Ability to work independently, take ownership, and act as a technical lead. • English proficiency: Intermediate or higher. What we offer • Office or remote — it's up to you. • Remote onboarding. • Performance bonuses for everyone (annual or quarterly — depends on the role). • We train employees: the opportunity to learn through the company’s own library, internal resources and programs from partners. • Health and life insurance. • Wellbeing program and corporate psychologist. • Reimbursement of expenses for Kyivstar mobile communication.