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# Senior Software Development Engineer

- **Company:** Mastercard
- **Location:** O'Fallon, MO, United States
- **Experience:** Expert
- **Salary:** $115,000.0 - $184,000.0
- **Contract:** Permanent contract
- **Skills:** Java (Programming Language), Computer-Aided Design, Artificial Intelligence, Application Performance Management, Automation of Tests, Code Review, Cyber Security, Continuous Integration, Distributed Systems, Java Persistence API, Scrum Methodology, Software Architecture, Systems Development Life Cycle, Secure Coding, Software Engineering, Spring Cloud, Multi-Agent Systems, Spring-boot, Software Security, Integration Tests, Solid Principles, Apache Kafka, Restful APIs, Code Restructuring, Microservices
- **Published:** October 31, 2026
- **Apply:** https://www.careerbuilder.com/job-details/senior-software-development-engineer-o-fallon-mo--0948a7e9-d4f3-4b6d-99d6-2b675a64a098

## About the Role

Software Development, Software Engineering, Software Development, Software Engineering, Mentoring, Distributed Computing, Production Support, Systems Scalability, Scalable System Development, Software Design, * Strong hands-on experience with Java, Spring Boot, Kafka, REST APIs, JPA, and distributed systems.

 * Strong understanding of software design and software architecture principles.
 * Experience building highly scalable and resilient systems.
 * Experience implementing automated testing strategies and quality engineering practices.
 * Strong knowledge of performance engineering and production optimization.
 * Strong understanding of secure software development principles.
 * Experience leading code reviews and mentoring engineers.
 * Strong troubleshooting and analytical problem-solving skills.
 * Experience with microservices, cloud-native applications, and CI/CD.
 * Experience building AI-assisted applications, autonomous agents, or agentic workflows.
 * Agile Scrum experience.

## Description

The Senior Software Development Engineer is a senior individual contributor responsible for designing, developing, and supporting highly scalable distributed systems. This role combines deep technical expertise with mentorship responsibilities and ownership of critical software components from design through production support.

What You Will Do

 * Design software solutions and contribute to software architecture decisions that support scalability, maintainability, and operational excellence.
 * Translate complex product requirements into technical designs and implementation plans.
 * Lead development of modular, extensible, high-performance applications.
 * Design and implement comprehensive unit, functional, and integration testing strategies.
 * Analyze, optimize, and improve application performance, scalability, and reliability.
 * Apply secure coding practices and promote application security best practices.
 * Lead and participate in code reviews, ensuring adherence to engineering standards.
 * Design systems with observability, operability, and supportability as core principles.
 * Research emerging frameworks and technologies and recommend adoption where appropriate.
 * Mentor junior developers and support onboarding activities.
 * Troubleshoot and resolve complex production issues using root cause analysis techniques.
 * Support engineering excellence through continuous improvement, refactoring, and adherence to SOLID principles., 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.