Senior Software Engineer

Join Mastercard's Transaction Stream team in O'Fallon, MO, and help build applications and services that power critical capabilities across the real-time payment network.

As a Senior Software Engineer, you will collaborate with engineers and product partners to design, build, test, and enhance solutions that support the movement of transactions around the world.

Responsibilities

• Design, develop, and maintain scalable test frameworks and automation solutions aligned with enterprise architecture standards
• Apply software design principles and architectural patterns to create maintainable and extensible testing and validation systems
• Contribute to system architecture discussions, ensuring solutions are testable, observable, secure, and performant
• Translate business and system requirements into well-designed technical solutions, test strategies, and validation models
• Ensure secure coding practices are embedded in development and testing processes, proactively identifying vulnerabilities and risks
• Develop and execute testing strategies across all levels: unit, functional, integration, system, and performance testing
• Leverage data structures and algorithms to optimize test execution, data handling, and performance validation
• Collaborate in Agile environments, contributing to backlog refinement, sprint planning, and design discussions

Software Engineering & Development

• Design, build, test, deploy, and maintain software components, automation frameworks, and validation tools
• Apply strong knowledge of data structures, algorithms, and efficient coding practices in building scalable solutions
• Contribute to end-to-end software development lifecycle, including design, development, testing, deployment, and monitoring

Architecture & Design

• Participate in defining software architecture and design patterns to ensure scalability, reliability, and maintainability
• Ensure systems are designed for testability, observability, performance, and operational readiness
• Provide input into microservices and cloud migration strategies

Quality Engineering & Testing

• Develop and implement test automation frameworks and CI/CD integration pipelines (e.g., Jenkins, XLR)
• Design comprehensive test strategies and plans, including performance, reliability, and production simulation testing
• Ensure high code quality and coverage using tools such as Sonar or Clover

Security & Compliance

• Apply and promote secure coding practices, including code analysis, vulnerability detection, and mitigation strategies
• Integrate security testing into CI/CD pipelines

Code Quality & Reviews

• Conduct and lead code reviews, ensuring adherence to coding standards, security practices, and maintainability
• Act as a technical reviewer for system designs, test strategies, and implementation approaches

Operability & Performance

• Ensure systems are observable, monitorable, and resilient across environments
• Perform performance engineering, including load testing, tuning, and bottleneck analysis
• Troubleshoot complex production issues and ensure rapid resolution

Collaboration & Leadership

• Partner with developers, architects, and product teams to drive engineering best practices
• Mentor junior engineers and contribute to knowledge sharing across teams
• Evaluate and recommend tools, technologies, and frameworks for continuous improvement

Requirements

• Experience building applications and REST APIs using Java, Spring Boot, and Spring Data JPA
• Strong foundation in computer science fundamentals, including data structures, algorithms, and object-oriented design
• Ability to write clean, secure, testable code and contribute to unit, service, and integration testing
• Comfort working with SQL and relational data concepts
• Strong analytical and problem-solving skills, with the ability to debug issues and identify practical solutions
• Strong verbal and written communication skills and the ability to work effectively in a collaborative team environment
• Self-motivated, organized, and eager to learn, with a passion for continuous improvement and delivering results
• Strong hands-on experience in software engineering, including development and quality engineering
• Proven experience working with testing across platforms, automation development, and CI/CD integration and deployment

Preferred Qualifications

• Experience in cloud and microservices architecture or mainframe modernization
• Experience designing systems for reliability, performance, and scalability
• Domain knowledge in payments and transaction processing systems
• Bachelor's or master's degree in computer science or equivalent experience