Lead 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
Lead Software Engineer
Overview:
Mastercard's Global Credit Authorization team is seeking a Lead Software Engineer to design, build, and validate mission-critical, highly available systems that process secure financial transactions at global scale.
In this role, you'll combine hands-on software engineering with deep quality engineering expertise to define and execute comprehensive validation strategies across functional behavior, transaction integrity, resiliency, performance, failover, recovery, monitoring, and production readiness. You'll develop software and automation using Java and/or Python, build and maintain representative test environments, and validate complex distributed systems under real-world traffic and failure conditions.
Working closely with software engineers, architects, operations teams, and cross-functional stakeholders, you'll troubleshoot software and networking issues, analyze defects, and ensure changes meet high standards for quality, reliability, performance, and operational readiness before production deployment.
You'll thrive in a collaborative, fast-paced Agile environment where software engineering, automation, resiliency, and continuous improvement are foundational to how we deliver technology.
This is a hybrid position based in O'Fallon, MO, requiring three days per week onsite.
Role:• Design, develop, and enhance software, test applications, utilities, and automation solutions using Java and/or Python to support system validation and engineering objectives.• Define and execute comprehensive validation strategies covering functional behavior, transaction integrity, performance, resiliency, failover, recovery, monitoring, and production readiness.• Build, configure, maintain, and troubleshoot lab and lower-level test environments that replicate production architecture, network configurations, traffic patterns, and system dependencies.• Apply knowledge of TCP/IP, persistent TCP connections, proxies, load balancers, routing, and network services to validate application and infrastructure behavior.• Develop and execute end-to-end functional, integration, regression, negative, failover, recovery, load, soak, and capacity testing for highly available distributed systems.• Design and implement automated testing frameworks and tools to improve quality, test coverage, repeatability, and engineering efficiency.• Validate traffic movement, transaction integrity, proxy bypass, rollback, and recovery procedures during maintenance, infrastructure changes, deployments, and failure scenarios.• Reproduce and troubleshoot complex issues by analyzing application code, logs, traces, metrics, network traffic, and packet captures, partnering with engineering teams to drive root-cause analysis and resolution.• Evaluate system performance, scalability, resiliency, capacity, and operational readiness under production-like workloads and failure conditions.• Define acceptance criteria, test evidence, certification documentation, validation reports, and production-readiness recommendations.• Collaborate with software engineers, architects, product owners, and operational teams throughout requirements analysis, design reviews, Agile ceremonies, testing, certification, and deployment activities.• Champion software engineering, quality, automation, and continuous-improvement best practices, identifying opportunities to strengthen tooling, environments, processes, and overall system reliability.
All About You:• Previous experience as a Senior or Lead Software Engineer, Software Developer, or Software Development Engineer in Test (SDET) working on complex enterprise systems.• Strong hands-on software development experience, including designing, developing, debugging, and maintaining production-quality applications, services, utilities, or automation.• Hands-on programming experience with Java and/or Python, including developing backend services, automation, test utilities, or frameworks.• Experience building, configuring, and troubleshooting test, lab, development, or lower-level environments for distributed applications.• Strong understanding of TCP/IP networking, persistent connections, routing, proxies, load balancers, DNS, ports, and network troubleshooting.• Experience analyzing packet captures, logs, traces, metrics, and operational telemetry to troubleshoot complex software and network issues.• Strong experience with functional, integration, resiliency, performance, and end-to-end testing of distributed or highly available systems.• Strong understanding of transaction-processing systems and validation of business-critical workflows and transaction integrity.• Proven experience with failover, recovery, disaster recovery, and business continuity testing for mission-critical systems.• Hands-on experience developing and using automated test frameworks, failure-injection methodologies, and performance testing tools.• Experience with load, stress, soak, scalability, and capacity testing for high-throughput applications and services.• Strong understanding of software engineering and quality practices, including test planning, certification, production readiness, and defect lifecycle management.• Demonstrated ability to perform root-cause analysis across software, infrastructure, and network layers and drive complex technical issues to resolution.• Strong analytical, problem-solving, technical documentation, and communication skills, with the ability to collaborate and influence across engineering, architecture, product, and operations teams.• Bachelor's degree in Computer Science, Software Engineering, Information Technology, Engineering, Mathematics, or a related field, or equivalent practical experience.
Preferred Experience:• Experience with financial messaging platforms, ISO 8583, payment switching systems, telecommunications platforms, or other high-availability transaction-processing environments.• Experience testing proxy, load-balancer, network-service, or active-active failover architectures.• Familiarity with large-scale distributed systems requiring stringent availability, resiliency, and performance requirements.• Experience supporting production certification and readiness activities for customer-facing transaction platforms.• Knowledge of observability, monitoring, and operational health validation practices for enterprise-scale services.
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 [email protected] 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.
THIS POSTING RELECTS ONE OR MORE CURRENT VACANCIES ON OUR TEAM, AND MASTERCARD INTENDS TO FILL THIS POSITION BY 01/20/2027. If the fill date has passed, Mastercard intends to fill this position as soon as possible.
Pay Ranges
O'Fallon, Missouri: $140,000 - $231,000 USD
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