Freelance Java Backend Developer Jobs in Saint Louis, MO

Description

If you’ve been building your skills in backend development, object‑oriented programming, and mission‑driven engineering, and you’re ready for work that actually moves the needle, this is the kind of opportunity cleared engineers pursue when they want to grow while making real impact. If you take pride in your craft, enjoy solving meaningful technical problems, and want your work to support a mission with visibility at senior levels, you’ll thrive here.

We’re hiring a Backend Software Engineer to support a high‑visibility, data‑driven application used across the organization for analytics and reporting. You’ll help build and maintain core backend services, develop RESTful APIs, support data‑driven functionality, and contribute to ongoing system enhancements within a Linux‑based environment. Your work will directly support system reliability, performance, and data accuracy for mission stakeholders. Our primary development team operates out of Gaithersburg, MD, but we also support onsite engineers in Chantilly, VA, Alexandria, 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 fare, 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 work supports a widely used application that drives real‑time decision‑making
• High Visibility: Collaborate with engineering teams and mission stakeholders across programs
• Career Growth: Build deeper expertise in backend development, API design, and scalable systems
• Challenging Work: Contribute to complex backend features — not routine maintenance tasks

Essential Responsibilities

• Backend Development: Design, develop, test, and maintain backend application components using Java or Python
• REST API Development: Develop and maintain RESTful services to support application functionality and system integrations
• Object-Oriented Programming: Apply object-oriented design principles to build scalable and maintainable systems
• Database Development: Write and modify SQL queries to support application functionality and data retrieval
• Data Source Collaboration: Collaborate with internal and external teams to understand data sources, formats, and access methods, and support integration into backend systems
• Linux Environments: Develop and troubleshoot applications within Linux-based environments
• Data Processing & Business Logic: Implement backend logic for data transformation, processing, and system workflows
• Bug Fixing & Enhancements: Identify, debug, and resolve application-level defects and performance issues
• Code Quality: Follow coding standards, participate in code reviews, and support documentation efforts

Basic Qualifications

• Bachelor’s degree in Computer Science, Software Engineering, or a related field with 4–8 years of experience; or a Master’s degree with 2–6 years of experience
• US Citizenship
• Active TS/SCI with the ability to successfully pass a Polygraph
• Professional experience developing object‑oriented applications in Java or Python
• Hands‑on experience building and maintaining RESTful APIs
• Basic to moderate experience with SQL capability, including writing queries and working with relational databases
• Working knowledge of Linux‑based environments
• Ability to work independently on defined tasks within established technical frameworks and deliver reliable results

Preferred Qualifications

• Experience with Apache Airflow or similar workflow orchestration technologies
• Experience with Spring Boot, Django, or similar backend frameworks
• Exposure to CI/CD pipelines (GitLab, Jenkins, etc.)
• Familiarity with containerization (Docker, OpenShift)
• Exposure to cloud environments (AWS or Azure)
• Experience working in Agile development environments

#NSBA

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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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