Top 106 Java software Jobs in O'fallon, Mo

Mid-Level Backend Software Engineer
Leidos —St. Louis, MO
- $87,100 - $157,450 a year
- Full-time
- Azure
- Computer Science
- System design
Mid-Level Software Engineer
Leidos —St. Louis, MO
- $87,100 - $157,450 a year
- Full-time
- Azure
- Computer Science
- Mid-level
14d
Lead Site Reliability Engineer
Mastercard —O'Fallon, MO
- $122,000 - $207,000 a year
- Online Application
- Computer science
- Computer Science
- Bachelor of Science
- Paid jury duty
- Health savings account
Lead Site Reliability Engineer-2
Mastercard —O'Fallon, MO
- $122,000 - $207,000 a year
- Online Application
- Computer science
- Computer Science
- Bachelor of Science
- Paid jury duty
- Health savings account
Senior Site Reliability Engineer
Mastercard —O'Fallon, MO
- $163,000 a year
- Online Application
- Computer Science
- Bachelor of Science
- System design
- Paid jury duty
- Health savings account
Software Engineer I
Mastercard —O'Fallon, MO
- $72,000 - $115,000 a year
- Online Application
- Computer science
- Computer Science
- System design
- Paid jury duty
- Health savings account
2d
Senior Site Reliability Engineer
Mastercard —O'Fallon, MO
- $96,000 - $163,000 a year
- Online Application
- Computer science
- Computer Science
- Bachelor of Science
- Paid jury duty
- Health savings account
Software Engineer IV – ERP Finance (Oracle/PLSQL)
SPECTRUM —St. Louis, MO
- $80,300 - $156,600 a year
- Computer Science
- System design
- English
- Opportunities for advancement
14d
Software Engineer II
Mastercard —O'Fallon, MO
- $92,000 - $147,000 a year
- Online Application
- System design
- Mid-level
- SQL
- Paid jury duty
- Health savings account
Java Developer (web services) - 100% Remote - Public Trust
ATTAINX INC —Saint Charles, MO
- $75,000 - $92,000 a year
- Remote
- Computer Science
- System design
- Mid-level
- Disability insurance
- Health insurance
1d
Senior Software Engineer
Mastercard —O'Fallon, MO
- $115,000 - $184,000 a year
- Online Application
- Computer science
- Computer Science
- System design
- Paid jury duty
- Health savings account
7d
Senior Software Engineer - Java Full Stack Engineer
Mastercard —O'Fallon, MO
- $115,000 - $184,000 a year
- Online Application
- Computer science
- 7 years
- Computer Science
- Paid jury duty
- Health savings account
Manager, Software Engineering
Mastercard —O'Fallon, MO
- $140,000 - $231,000 a year
- Online Application
- Computer Science
- Writing skills
- Engineering
- Paid jury duty
- Health savings account
8d
Senior Software Development Engineer
Mastercard —O'Fallon, MO
- $115,000 - $184,000 a year
- Online Application
- Research
- Analysis skills
- Mentoring
- Paid jury duty
- Health savings account
6d
Software Developer (mid-level) - 100% Remote - Public Trust
ATTAINX INC —Saint Charles, MO
- $75,000 - $92,000 a year
- Remote
- Computer Science
- System design
- Mid-level
- Disability insurance
- Health insurance
Quick Apply
22h
Software Developer II - Financials (Full Stack, Front End)
National Information Solutions Cooperative (NISC) —Lake Saint Louis, MO
- Hybrid work
- Computer science
- Computer Science
- Customer service
- Health savings account
- Paid holidays
2d
Java Engineer
J2B Global LLC —O'Fallon, MO
- Azure
- 8 years
- SQL
9d
Lead Software Engineer
Mastercard —O'Fallon, MO
- $140,000 - $231,000 a year
- Online Application
- Hybrid work
- Computer science
- Computer Science
- Office
- Paid jury duty
- Health savings account
Manager Software Engineering
Mastercard —O'Fallon, MO
- $140,000 - $231,000 a year
- Online Application
- Computer science
- Computer Science
- System design
- Paid jury duty
- Health savings account
Software Engineer
HSTechnologies —Chesterfield, MO
- Email
- Computer science
- Azure
- Computer Science

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Mid-Level Backend Software Engineer

Leidos -
St. Louis, MO

Apply Now

Job Details

Full-time
$87,100 - $157,450 a year

Qualifications

SQL
Linux
Query management

Full Job Description

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

#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.

Original Posting:

April 16, 2026

For U.S. Positions: While subject to change based on business needs, Leidos reasonably anticipates that this job requisition will remain open for at least 3 days with an anticipated close date of no earlier than 3 days after the original posting date as listed above.

Pay Range:

Pay Range $87,100.00 - $157,450.00

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 [email protected].

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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Refine Your Search

java software jobs in o'fallon, mo

Mid-Level Backend Software Engineer

Mid-Level Software Engineer

Lead Site Reliability Engineer

Lead Site Reliability Engineer-2

Senior Site Reliability Engineer

Software Engineer I

Senior Site Reliability Engineer

Software Engineer IV – ERP Finance (Oracle/PLSQL)

Software Engineer II

Java Developer (web services) - 100% Remote - Public Trust

Senior Software Engineer

Senior Software Engineer - Java Full Stack Engineer

Manager, Software Engineering

Senior Software Development Engineer

Software Developer (mid-level) - 100% Remote - Public Trust

Software Developer II - Financials (Full Stack, Front End)

Java Engineer

Lead Software Engineer

Manager Software Engineering

Software Engineer

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