Senior System Administrator

About the role

Radiant, a startup developing portable nuclear microreactors, is looking for a Senior System Administrator to own and operate its Microsoft 365 GCC High environment and related identity, endpoint, email security, and SaaS infrastructure. The role is highly autonomous and integral to the company’s CMMC compliance and overall IT operations.

Key responsibilities

• Administer Microsoft 365 GCC High services (Exchange Online, SharePoint, Teams) and serve as the authority on cloud capabilities.
• Design and implement Entra‑based identity and access management, including conditional access, privileged access, app registrations, and automated joiner/mover/leaver workflows using Graph and SCIM.
• Manage Windows endpoint lifecycle via Intune, Autopilot, compliance policies, and update rings without on‑prem Group Policy.
• Configure email security and information protection with Defender for Office, mail flow rules, and Purview DLP, labeling, and retention.
• Administer SaaS applications such as Box and Slack and oversee AWS workloads in coordination with the IT DevOps engineer.
• Lead platform projects from concept through deployment, documentation, and compliance evidence collection for CMMC assessments.

Required profile

• Bachelor’s degree in IT, Computer Engineering, Cybersecurity or equivalent experience (4 years replaces degree).
• 7+ years of production system administration and engineering.
• Deep hands‑on experience with GCC High tenant, Entra, IAM automation, Intune, email security, Purview, and AWS SaaS administration.
• Solid networking fundamentals (VLANs, routing, firewalls, DNS/DHCP, VPN, wireless).

Required skills

• Microsoft 365 GCC High, Exchange Online, SharePoint, Teams
• Azure Entra ID, conditional access, privileged access, app registrations, SSO
• IAM automation via PowerShell, Python, Microsoft Graph, SCIM
• Intune, Autopilot, compliance policies, update rings
• Defender for Office, Purview DLP, sensitivity labeling, retention
• AWS services administration
• Box, Slack integration in regulated environments
• Infrastructure as code (Terraform, Bicep)
• Networking (VLAN, routing, firewall, DNS/DHCP, VPN, wireless)

What we offer

• Substantial incentive stock plan for all full‑time employees
• Comprehensive medical, vision, dental, and life benefits with high employer contribution
• Sponsored One Medical memberships for employees and dependents
• 8 weeks paid parental leave and additional paid pregnancy leave for CA employees
• Daily catered lunch, free snacks and drinks
• Flexible PTO and allocated remote workday
• Team‑building events and a modern El Segundo headquarters near the Pacific Ocean