Senior Software Engineer

Mastercard•O'fallon, MO

1d•$115,000 - $184,000•Onsite

About The Position

Mastercard's Core Payments engineering teams build and support the platforms responsible for secure, reliable, and scalable payment capabilities around the world. This Senior Full Stack Software Engineer will contribute to mission-critical solutions that support Foreign Exchange rate setting across Mastercard, including external APIs clients use to access exchange rates and internal services that help power high-impact payment operations. Working closely with product managers, business stakeholders, and engineering teams, you will design and deliver new features, strengthen automated testing practices, and improve the efficiency, quality, and stability of systems operating at global scale. This role is well suited for a software engineer who can move across front-end, back-end, APIs, and automated integration testing while staying curious, collaborative, and quick to respond when something breaks during development.

Requirements

Strong proficiency in Java, Spring Boot, Jakarta Persistence API/JPA, and REST-based services using JSON and XML.
Proven ability to build automated unit, functional, integration, and regression testing solutions, with a clear understanding of why automation matters for mission-critical systems.
Ability to work across APIs, web applications, and full stack development, with Angular or a similar front-end framework strongly preferred; React is also relevant.
Curious, humble, and open to new ideas, with the confidence to ask questions, learn quickly, and support a collaborative team environment.
Ability to design scalable software solutions that balance performance, maintainability, security, and operational reliability.
Familiarity with distributed systems, service-oriented architectures, and modern software design patterns.
Strong understanding of software quality principles, test strategy development, and automation frameworks such as JUnit.
Knowledge of CI/CD practices and automated delivery pipelines.
Ability to evaluate code quality, identify improvement opportunities, and contribute to a culture of continuous improvement.
Strong troubleshooting and analytical skills with the ability to diagnose and resolve complex technical issues.
Understanding of performance engineering concepts, including scalability, throughput, and optimization techniques.
Commitment to secure coding practices and development standards that support highly available enterprise applications.
Solid understanding of data structures and algorithms and their application to real-world engineering challenges.
Effective communication skills with the ability to collaborate across engineering, product, program management, and business teams.
Comfortable balancing multiple priorities while delivering high-quality solutions in a fast-paced Agile environment.
Familiarity with Agile methodologies and tools such as Jira.

Nice To Haves

Angular or a similar front-end framework strongly preferred; React is also relevant.

Responsibilities

Design, develop, and enhance full stack applications, APIs, and services that support Mastercard's Core Payments and Foreign Exchange rate-setting capabilities.
Deliver new features from design sessions and team planning through implementation, automated testing, release support, and ongoing enhancement.
Build and maintain automated unit, functional, integration, and regression tests that improve release speed and help the team quickly identify issues during development.
Support work that is approximately 10% design sessions and team meetings, 60% software implementation, and 30% automated integration testing and development.
Build business and product knowledge over time, becoming a trusted resource within the team while helping newer engineers learn, ask questions, and grow.
Translate business and product requirements into scalable, maintainable solutions that meet functional and non-functional requirements.
Define acceptance criteria, testing strategies, and quality standards that promote stable and predictable releases.
Participate in requirements reviews, sprint planning, and technical discussions to deliver incremental value throughout the development lifecycle.
Create and maintain technical designs, user stories, and test cases using Jira.
Contribute to architecture discussions, helping shape solutions that prioritize performance, resiliency, maintainability, and security.
Review code, provide constructive feedback, and promote engineering practices that improve software quality and reduce technical debt.
Analyze system behavior, troubleshoot production issues, perform root-cause analysis, and implement long-term corrective actions.
Enhance operational readiness through monitoring, observability, recoverability, and supportability improvements.
Identify opportunities to optimize application performance and scalability while supporting service-level objectives.

Benefits

insurance (including medical, prescription drug, dental, vision, disability, life insurance)
flexible spending account and health savings account
16 weeks of new parent leave
up to 20 days of bereavement leave
80 hours of Paid Sick and Safe Time
25 days of vacation time
5 personal days
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