Junior Java Software Engineer Jobs in Bridgeton, MO

Our Purpose
Mastercard powers economies and empowers people in 200+ countries and territories worldwide. Together with our customers, we're helping build a sustainable economy where everyone can prosper. We support a wide range of digital payments choices, making transactions secure, simple, smart and accessible. Our technology and innovation, partnerships and networks combine to deliver a unique set of products and services that help people, businesses and governments realize their greatest potential.
Title and Summary
Senior Software Engineer
Who We Are
Mastercard powers economies and empowers people in 200+ countries and territories worldwide. Together with our customers, we're helping build a sustainable economy where everyone can prosper. We support a wide range of digital payments choices, making transactions secure, simple, smart, and accessible. Our technology and innovation, partnerships, and networks combine to deliver a unique set of products and services that help people, businesses, and governments realize their greatest potential.
Overview
The CORE Payments Optimization team is seeking a Senior Software Engineer to build and enhance critical payment processing services that support issuer account management, transaction controls, and card lifecycle management across Mastercard's global network.
This role is ideal for an experienced software engineer who enjoys solving complex distributed systems challenges, designing scalable event-driven solutions, and working with high-volume payment processing applications. The successful candidate will contribute across the full software development lifecycle, from architecture and design through implementation, testing, deployment, optimization, and operational support.
The position requires strong expertise in Java-based application development, Spring Boot, Kafka, PostgreSQL, and modern software engineering practices, along with the ability to influence technical direction and mentor other engineers.
Role
As a Senior Software Engineer, you will:
• Design, develop, test, deploy, and support scalable software solutions that power Mastercard's payment processing ecosystem.
• Build and maintain event-driven applications utilizing Kafka and distributed messaging patterns to process high-volume transaction workloads.
• Develop microservices and backend services using Java, Spring Boot, and Spring Batch frameworks.
• Design database solutions utilizing PostgreSQL and optimize data access patterns for performance, reliability, and scalability.
• Contribute to software architecture decisions and help modernize existing applications through scalable, maintainable engineering practices.
• Analyze business and technical requirements and translate them into robust software designs that balance functionality, performance, security, and operational excellence.
• Create and maintain comprehensive unit, functional, and integration tests to ensure software quality and reliability.
• Conduct code reviews and provide constructive feedback to improve software quality, maintainability, and adherence to engineering standards.
• Troubleshoot and resolve complex application, system, and production issues across distributed platforms.
• Apply secure coding practices and proactively address security vulnerabilities throughout the software development lifecycle.
• Collaborate with Product, Architecture, Platform Engineering, Operations, and partner teams to deliver enterprise-scale solutions.
• Design systems with observability in mind by implementing logging, monitoring, metrics, and alerting capabilities that improve operational readiness.
• Optimize applications and services to meet performance, scalability, availability, and reliability objectives.
• Support production readiness activities, incident management, root cause analysis, and continuous improvement initiatives.
• Mentor and coach engineers through technical leadership, knowledge sharing, and engineering best practices.
• Continuously evaluate emerging technologies and engineering approaches that improve development productivity and platform capabilities.
All About You
Required Qualifications
• Strong experience developing enterprise applications using Java and Spring Boot.
• Experience building event-driven architectures utilizing Kafka or similar messaging technologies.
• Strong understanding of software development principles, object-oriented programming, and distributed systems.
• Experience designing and developing REST APIs and microservices architectures.
• Hands-on experience with PostgreSQL or other relational database platforms.
• Experience implementing automated testing strategies including unit, functional, and integration testing.
• Strong troubleshooting and root cause analysis capabilities within complex production environments.
• Experience conducting code reviews and promoting engineering best practices.
• Knowledge of secure coding principles and application security standards.
• Experience optimizing application performance, scalability, and reliability.
• Strong understanding of software design patterns, data structures, and algorithms.
• Excellent communication, collaboration, and problem-solving skills.
Preferred Qualifications
• Experience with Spring Batch processing frameworks.
• Experience supporting mission-critical transaction processing systems.
• Familiarity with cloud platforms and containerized deployments.
• Experience with CI/CD pipelines and DevOps engineering practices.
• Knowledge of observability tooling, application monitoring, and operational excellence practices.
• Experience within financial services, payments, or highly regulated environments.
Mastercard is a merit-based, inclusive, equal opportunity employer that considers applicants without regard to gender, gender identity, sexual orientation, race, ethnicity, disabled or veteran status, or any other characteristic protected by law. We hire the most qualified candidate for the role. In the US or Canada, if you require accommodations or assistance to complete the online application process or during the recruitment process, please contact reasonable_accommodation@mastercard.com and identify the type of accommodation or assistance you are requesting. Do not include any medical or health information in this email. The Reasonable Accommodations team will respond to your email promptly.
Corporate Security Responsibility
All activities involving access to Mastercard assets, information, and networks comes with an inherent risk to the organization and, therefore, it is expected that every person working for, or on behalf of, Mastercard is responsible for information security and must:

• Abide by Mastercard's security policies and practices;
• Ensure the confidentiality and integrity of the information being accessed;
• Report any suspected information security violation or breach, and
• Complete all periodic mandatory security trainings in accordance with Mastercard's guidelines.

In line with Mastercard's total compensation philosophy and assuming that the job will be performed in the US, the successful candidate will be offered a competitive base salary and may be eligible for an annual bonus or commissions depending on the role. The base salary offered may vary depending on multiple factors, including but not limited to location, job-related knowledge, skills, and experience. Mastercard benefits for full time (and certain part time) employees generally include: insurance (including medical, prescription drug, dental, vision, disability, life insurance); flexible spending account and health savings account; paid leaves (including 16 weeks of new parent leave and up to 20 days of bereavement leave); 80 hours of Paid Sick and Safe Time, 25 days of vacation time and 5 personal days, pro-rated based on date of hire; 10 annual paid U.S. observed holidays; 401k with a best-in-class company match; deferred compensation for eligible roles; fitness reimbursement or on-site fitness facilities; eligibility for tuition reimbursement; and many more. Mastercard benefits for interns generally include: 56 hours of Paid Sick and Safe Time; jury duty leave; and on-site fitness facilities in some locations.
Pay Ranges
O'Fallon, Missouri: $115,000 - $184,000 USD