Junior Software Engineer In Test Jobs in St Louis, MO

Our Purpose

Mastercard powers economies and empowers people in 200+ countries and territories worldwide. Together with our customers, we're helping build asustainableeconomy where everyone can prosper. We support a wide range of digital payments choices, making transactionssecure, 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 EngineerWho 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
As part of a fast-paced team building authentication and security solutions, you will help design and deliver secure, scalable, and high-performing software for Mastercard's Identity Solutions platform.
As a Senior Software Engineer, you'll take ownership of complex technical work, contribute to design and architecture decisions, and support the team in delivering reliable, production-ready systems. You'll collaborate closely with product, security, and platform teams to build solutions that meet both business and technical needs.
Role
Design, build, test, deploy, and maintain scalable, cloud-native applications and microservices
Develop REST APIs using Java and Spring Boot, focusing on performance, scalability, and reliability
Translate requirements into well-structured designs and architecture, ensuring maintainability and security
Lead and contribute to system design discussions, aligning with architectural standards and best practices
Write and maintain unit, functional, and integration tests to ensure quality and reliability
Drive improvements in test automation, code coverage, and system reliability
Analyze and optimize system performance, scalability, and efficiency
Apply secure coding practices and lead vulnerability remediation efforts (CVE remediation, upgrade automation)
Perform and lead code reviews to improve code quality, maintainability, and adherence to standards
Troubleshoot and resolve complex production issues using structured problem-solving and root cause analysis
Ensure systems are built with strong operability (monitoring, logging, reliability, support readiness)
Contribute to CI/CD pipelines and engineering practices that improve delivery speed and quality
Collaborate across teams (product, QA, platform) to deliver high-quality solutions
Mentor junior engineers and support knowledge sharing across the team
Contribute to a culture of continuous improvement, accountability, and collaboration
All About You
Experience building RESTful services using Java and Spring Boot
Strong experience designing scalable systems using modern software design and architecture principles
Experience with cloud platforms (AWS, Azure, or GCP) and containerization (Docker, Kubernetes)
Proven ability to work independently on complex technical problems and support team outcomes
Experience writing and maintaining unit, functional, and integration tests
Strong understanding of performance engineering (analyzing and optimizing systems at scale)
Expertise in secure coding practices and vulnerability management
Experience leading and contributing to code reviews and engineering standards
Strong troubleshooting and root cause analysis skills in complex environments
Solid understanding of data structures and their impact on performance and scalability
Experience building systems with strong operability, monitoring, and reliability practices
Experience working in Agile/Scrum environments and collaborating across teams
Strong communication and collaboration skills, with the ability to influence technical decisions
Experience mentoring or supporting other engineers
Bachelor's degree or equivalent experience
Nice to Have
Knowledge of event-driven architectures (Kafka or similar)
Experience in high-throughput or regulated environments (payments, banking, fintech)
Exposure to AI/automation tools within software development workflows
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.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 reasonable_accommodation@mastercard.com 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.

Pay Ranges

O'Fallon, Missouri: $115,000 - $184,000 USD