Senior API Developer

General information

Requisition # R65337 Locations USA-VA-Chantilly Posting Date 01/27/2026 Security Clearance Required TS/SCI w/ Poly Remote Type Onsite Time Type Full time

Description & Requirements

Elevate your career with MANTECH International Corporation! Join a dynamic team dedicated to national security through cutting-edge technology. Since 1968, MANTECH has led in delivering advanced solutions to government intelligence, the Department of Defense, and Federal Civilian sectors. Dive into innovation in Digital Transformation, Cybersecurity, IT, Data Analytics and Software Development. Your journey to impactful work and rapid growth starts now—be extraordinary at MANTECH!

MANTECH seeks an experienced Senior API Developer to design, build, and maintain mission-critical integrations using MuleSoft. You will be a key member of a six-person team supporting the integration, deployment and production sustainment of the MuleSoft Private Cloud Edition (PCE) solution supporting a key Intelligence Community (IC) customer. This position is based in Chantilly, VA

In this hands-on role, you will apply API-led connectivity principles to connect diverse enterprise systems, including Salesforce, on-prem, cloud services or other SaaS platforms. You will work within a fast-paced Agile (Scrum) environment to rapidly deliver new features, integrate security (DevSecOps) at every step, and ensure the operational stability of the platform.

Responsibilities include but are not limited to:

• Design, build, test, and deploy robust, secure, and reusable APIs and integrations.

• Serve as a subject matter expert on API-led connectivity, runtime management, and connector configuration.

• Develop and deploy new APIs, connectors, and data transformations based on prioritized requirements from the product backlog.

• Conduct static/dynamic code analysis and vulnerability scanning to ensure secure code.

• Perform comprehensive unit, integration, and performance testing to ensure the quality and reliability of all new features.

• Provide on-call Tier 2/3 support for platform-related incidents and service requests related to API performance or errors, as needed.

• Support security accreditation (RMF/ATO) activities by implementing required security controls and remediating findings from the Plan of Action & Milestones (POA&M), as needed.

Minimum Qualifications:

• 6+ years of hands-on software development experience for an IC customer

• 6+ years of experience in a customer facing role supporting an IC customer

• 5+ years of experience designing and building secure, robust, and reusable RESTful APIs using API-led connectivity principles.

• 5+ years hands-on experience programming in Java

• Familiarity with DevSecOps practices, including CI/CD pipelines, static/dynamic code analysis, and vulnerability scanning.

• Strong understanding of integration patterns, data transformations, error h