Principal Systems Engineer; API Gateway - TS​/SCI w CI Poly

TITLE: Principal Systems Engineer (API Gateway)

LOCATION: Sterling, VA

CLEARANCE REQUIRED: Active TS/SCI with CI Poly

EMPLOYMENT TYPE: Full-time, Onsite

Modern Government Solutions (MGS) is seeking a Principal Systems Engineer to architect, integrate, and secure mission‑critical API ecosystems supporting next‑generation national security capabilities. In this role, you will lead the design and implementation of API gateway solutions, cloud‑native integrations, and enterprise service architectures that enable secure data exchange across complex environments. Working alongside software engineers, cloud architects, cybersecurity professionals, and mission stakeholders, you will help modernize critical systems through scalable APIs, automation, and cloud technologies.

The ideal candidate brings deep expertise in API platforms, cloud architecture, systems integration, and troubleshooting complex enterprise environments while maintaining the engineering rigor required to support high‑impact mission operations.

• Design, implement, and sustain enterprise API gateway solutions and service architectures supporting secure system integration across mission environments.
• Architect and support cloud‑based integrations utilizing APIs, message queues, streaming platforms, ETL pipelines, and related technologies.
• Support Windows‑based platforms, COTS applications, and cloud‑hosted systems within secure enterprise environments.
• Troubleshoot complex application, infrastructure, and integration issues, performing root cause analysis and implementing corrective actions.
• Develop and execute system testing, validation, and performance assessment activities to ensure operational readiness and reliability.
• Collaborate with engineering, cybersecurity, infrastructure, and mission stakeholders to implement technical solutions and architectural improvements in a Scaled Agile Framework environment.
• Participate in Program Increment and Sprint planning, to include t‑shirt sizing, story point estimation, and dependency mapping.
• Evaluate emerging technologies and recommend enhancements to API platforms, cloud architectures and infrastructure configurations, and enterprise integration capabilities.
• Create and maintain technical documentation, architecture artifacts, implementation guides, and operational procedures.
• Provide technical leadership and engineering guidance across API platform, cloud, and integration initiatives.
• Ability to remain in a stationary position for extended periods while working at a computer workstation.
• Ability to communicate effectively with customers, team members, and stakeholders in both written and verbal formats.

• Must possess an active DoD TS/SCI security clearance with CI Polygraph.
• Must meet DoD 8140 requirements, including Security+ CE certification.
• Bachelor's degree in Systems Engineering, Computer Science, Computer Engineering, Software Engineering, Information Technology, Electrical Engineering, Mathematics, Physics, or a related field.
• 16+ years of experience designing, integrating, and supporting enterprise systems, cloud architectures, and API‑driven solutions within complex mission environments.
• 5+ years of experience implementing and administering API gateway technologies in cloud‑based architectures.
• Experience designing secure APIs and enterprise integration solutions utilizing REST, GraphQL, event‑driven architectures, message queues, streaming platforms, or ETL pipelines.
• Experience supporting Windows‑based platforms, COTS applications, and cloud environments utilizing AWS or Azure.
• Experience developing software, automation, or integration solutions using Java, Python, C#, or similar programming languages, with demonstrated expertise in testing, validation, troubleshooting, root‑cause analysis, and technical documentation.
• This position requires regular onsite attendance at our Sterling, VA facility. Candidates must be able to reliably commute to the facility each workday and, when operational needs require, report to the facility within 60 minutes.

• Experience supporting Broadcom API…