Senior Software Engineer

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 is Mastercard?

Mastercard is a global technology company in the payments industry. Our mission is to connect and power an inclusive, digital economy that benefits everyone, everywhere by making transactions safe, simple, smart, and accessible. Using secure data and networks, partnerships and passion, our innovations and solutions help individuals, financial institutions, governments, and businesses realize their greatest potential.

Our decency quotient, or DQ, drives our culture and everything we do inside and outside of our company. With connections across more than 210 countries and territories, we are building a sustainable world that unlocks priceless possibilities for all.

About the Role

Join Mastercard’s Transaction Stream team in O’Fallon, MO, and help build the applications and services that power critical capabilities across the real-time payment network. This is an opportunity to work on software that operates at global scale, where speed, reliability, and resilience matter every day. 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.

Role

As a Senior Software Engineer, you will:

• 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

Responsibilities

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 & Leaders