The Senior Systems Administrator serves as a senior technical lead in a complex mixed Windows/Linux enterprise environment. This role is responsible for the administration, security, sustainment, and improvement of core infrastructure and hosted services, including server platforms, virtualization, storage, databases, web and application hosting, and identity services. The ideal candidate is an experienced enterprise administrator with broad technical depth, strong operational judgment, and the ability to provide technical leadership, mentorship, and escalation support in a compliance-driven environment.