Senior Software Engineer I (SE4 - St. Louis, MO)

Overview

Senior Software Engineer I (SE4 - St. Louis, MO)

Job ID: 2026-128 Date Posted: 2026-03-26
Location: St. Louis, Missouri
Minimum Experience: 10 years
Education: Master\'s Degree

Epsilon C5I ( a division of Epsilon Systems Solutions, is a 100 percent employee-owned company founded in 1998 with more than 20 locations serving the Department of Defense, Department of Energy, Department of Homeland Security, non-profit and commercial customers. The Dayton division has recently been named as one of only five prime awardees for the 10-year, $4.7 billion NOVASTAR contract supporting the National Air and Space Intelligence Center (NASIC), WPAFB, Ohio. The Dayton division has added over 70 full-time employees in just three years and are making plans now to exceed 100 full-time employees by this time next year. We are looking for talented individuals with a passion to serve their nation as we take on the challenges facing the country from threats around the world. Are you ready?

We're seeking a skilled Senior Full Stack Developer I or Senior DevSecOps Engineer I to join our dynamic team in St. Louis, MO, building secure, scalable, and high-performance applications. The ideal candidate will bring a strong foundation in software development alongside a keen understanding of secure coding practices, automation, and deployment pipelines. Whether you\'re passionate about writing clean, maintainable code across the frontend and backend, or you\'re focused on integrating security into CI/CD workflows, infrastructure as code, and cloud-native environments, we value your ability to work collaboratively across development, operations, and security teams. You’ll play a key role in driving innovation, ensuring software quality, and embedding security throughout the development lifecycle. Candidates must be able to work independently and as part of a technical team and have effective oral and written communication skills. Successful candidates will have strong problem solving and critical thinking skills. Desire an active TS/SCI clearance. Hybrid and remote work available.

Duties and Responsibilities:

• Applying advanced knowledge software engineering, computer science and information technology experience and expertise toward the technical design, development, and implementation of complex programming tasks will require exceptional initiative and independent judgement.
• Writing skills are necessary to support the continual development of both technical reports and documentation for the other members of the Team and to develop the overall product documentation our client expects as part of the final deliverable.
• Identify, captures, understands, translates, and document customer requirements.
• Defines system and product requirements.
• Manages and documents system configurations, and oversees all transitions into production.
• Performs troubleshooting and remediation, ensures successful project implementation, and performs post project end user support.
• Deploy new secure systems and networks.
• Conduct post processing and data reduction.
• Must have a practical working knowledge of the Scrum framework, as well as experience working on a Scrum Team.
• Write analysis reports and develop briefings.
• Work independently and in a team environment.
• Produce well-written designed, testable and efficient code that meet and exceed technical requirements.
• Actively contribute to a highly collaborative team environment, throughout all phases of the development lifecycle.
• Deploy applications on classified and secured networks.
• Deliver projects on time and with attention to quality.

Required Qualifications:

• Master of Science degree in engineering, computer science, or information technology.
• 10 or more years of relevant experience.
• Hands on experience with React and TypeScript/JavaScript.
• Good interpersonal skills and the ability to communicate with all levels of business users and management.
• Ability to work individually and on team projects in an environment of teamwork and cooperation.
• Effective written, oral, and presentation skills.
• Applicants must be willing and able to obtain DoD Top Secret security clearance, with SCI access eligibility.
• Pursuant to the various government contractual requirements, all applicants must be U.S. Citizens.

Desired Qualifications:

• CI/CD tools (e.g., Jenkins, GitLab CI).
• Cloud security (AWS, Azure, GCP).
• Container security (Docker, Kubernetes).
• Threat modeling, secure coding practices.
• Scripting (Python, Bash).
• Frontend: React, Angular, Vue, etc.
• Backend: Node.js, Django, Spring Boot, etc.
• Databases: SQL (PostgreSQL, MySQL), NoSQL (MongoDB).
• RESTful APIs, GraphQL.
• Git, Docker
• Experience with RHEL and CENTOS.

ADA Notations:

• Regular communication (hearing/speaking).
• Noise conditions range from very quiet to very noisy.
• Prolonged use of computer (typing/keyboarding).
• Frequently required to sit for long periods of time, stand, and walk.
• Ability to travel by car, air or other means of transportation, if required.

Epsilon Systems Solutions, Inc. is an equal opportunity employer. Qualified candidates will be considered without regard to legally protected characteristics.

Equal employment opportunity, including veterans and individuals with disabilities.