Senior Java Backend Developer Jobs in Belleville, IL

Description

If you’ve spent the last few years building your expertise in backend engineering, Java or Python development, and mission‑driven systems, and you’re ready for work that actually moves the needle, this is the kind of opportunity cleared engineers pursue when they want real impact. If you take pride in your craft, write your own résumé, and deliver results that senior leaders actually see, you’ll thrive here.

We’re hiring a Backend Software Engineer to support a high‑visibility application relied on across the organization for data analysis, reporting, and operational decision‑making. You’ll design and build scalable backend services, develop RESTful APIs, integrate complex data sources, and ensure system reliability and performance in a Linux‑based environment.

Our primary development team operates out of Gaithersburg, MD, but we also support onsite engineers in Alexandria, VA; Chantilly, VA; Aurora, CO; St. Louis, MO; and Tucson, AZ, giving top talent multiple paths to join the mission.

And while the requisition requirements may seem standard fair, the position is not; as it will join a high performing team that is changing the way digital engineering and mission operations intelligence is enabled for our customer. 

Why This Role Stands Out

• High Impact: Your services power a widely used application that drives real‑time decisions

• High Visibility: Collaborate directly with engineering teams and mission stakeholders

• Career Growth: Deepen your expertise in backend architecture, API design, and scalable systems

• Challenging Work: Build and optimize complex backend features

Key Responsibilities

• Backend Development: Design, develop, test, and maintain backend services using Java or Python

• REST API Development: Design and implement RESTful services to support application functionality and integrations

• Object-Oriented Design: Apply strong object-oriented design principles to build scalable and maintainable systems

• Database Development: Write and optimize SQL queries to support application functionality and performance

• Data Source Integration Coordination: Coordinate with external teams to understand data sources, interfaces, and access patterns, and translate requirements into backend integrations

• System Design Contribution: Participate in technical design discussions and contribute to backend architecture decisions

• Linux Environments: Develop, deploy, and troubleshoot applications within Linux-based environments

• System Troubleshooting: Diagnose and resolve issues across application and database layers

• Code Quality & Best Practices: Participate in code reviews and ensure adherence to engineering standards

Basic Qualifications

• Bachelor’s degree in Computer Science, Software Engineering, or a related field with 8–12 years of experience; or a Master’s degree with 6–10 years of experience

• U.S. Citizenship

• Active TS/SCI clearance with the ability to successfully pass a Polygraph

• Strong professional experience developing backend applications in Java or Python

• Proven ability to design and develop RESTful APIs that support scalable application functionality

• Solid SQL experience, including writing and optimizing queries across relational databases

• Confident working in Linux‑based environments

• Ability to work independently and drive solutions to moderately complex and complex technical challenges

Preferred Qualifications

• Experience with Apache Airflow or similar workflow orchestration technologies

• Experience with geospatial data and querying (e.g., PostGIS)

• Experience with Spring Boot, Django, or similar backend frameworks

• Experience with CI/CD pipelines (GitLab, Jenkins, etc.)

• Familiarity with containerization (Docker, OpenShift, Kubernetes)

• Exposure to cloud environments (AWS or Azure)

• Experience working in Agile development environments

#MARU

If you're looking for comfort, keep scrolling. At Leidos, we outthink, outbuild, and outpace the status quo — because the mission demands it. We're not hiring followers. We're recruiting the ones who disrupt, provoke, and refuse to fail. Step 10 is ancient history. We're already at step 30 — and moving faster than anyone else dares.

The Leidos pay range for this job level is a general guideline only and not a guarantee of compensation or salary. Additional factors considered in extending an offer include (but are not limited to) responsibilities of the job, education, experience, knowledge, skills, and abilities, as well as internal equity, alignment with market data, applicable bargaining agreement (if any), or other law.

About Leidos

Leidos is an industry and technology leader serving government and commercial customers with smarter, more efficient digital and mission innovations. Headquartered in Reston, Virginia, with 47,000 global employees, Leidos reported annual revenues of approximately $16.7 billion for the fiscal year ended January 3, 2025. For more information, visit www.Leidos.com.

Pay and Benefits

Pay and benefits are fundamental to any career decision. That's why we craft compensation packages that reflect the importance of the work we do for our customers. Employment benefits include competitive compensation, Health and Wellness programs, Income Protection, Paid Leave and Retirement. More details are available at www.leidos.com/careers/pay-benefits.

Securing Your Data

Beware of fake employment opportunities using Leidos’ name. Leidos will never ask you to provide payment-related information during any part of the employment application process (i.e., ask you for money), nor will Leidos ever advance money as part of the hiring process (i.e., send you a check or money order before doing any work). Further, Leidos will only communicate with you through emails that are generated by the Leidos.com automated system – never from free commercial services (e.g., Gmail, Yahoo, Hotmail) or via WhatsApp, Telegram, etc. If you received an email purporting to be from Leidos that asks for payment-related information or any other personal information (e.g., about you or your previous employer), and you are concerned about its legitimacy, please make us aware immediately by emailing us at LeidosCareersFraud@leidos.com.

If you believe you are the victim of a scam, contact your local law enforcement and report the incident to the U.S. Federal Trade Commission.

Commitment to Non-Discrimination

All qualified applicants will receive consideration for employment without regard to sex, race, ethnicity, age, national origin, citizenship, religion, physical or mental disability, medical condition, genetic information, pregnancy, family structure, marital status, ancestry, domestic partner status, sexual orientation, gender identity or expression, veteran or military status, or any other basis prohibited by law. Leidos will also consider for employment qualified applicants with criminal histories consistent with relevant laws.

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