This position is listed on behalf of a partner company, who manages all applications and next steps. Our partner is looking for a Senior Software Engineer/Developer based in the United States. This role supports the modernization, integration, and sustainment of mission-critical IT systems within a federal environment. You will contribute to the design and development of secure, scalable applications while helping migrate legacy capabilities to modern platforms. The position combines hands-on software engineering, application integration, DevOps, cybersecurity, testing, and technical documentation. You will collaborate with engineers, developers, analysts, security teams, and government stakeholders to deliver reliable solutions aligned with organizational requirements. The role also provides an opportunity to advance CI/CD practices, cloud-native architectures, automation, and secure software development. Strong technical judgment, adaptability, and a commitment to quality will be essential in this highly collaborative environment.