Senior Reliability Engineer Jobs in O Fallon, MO

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 Site Reliability Engineer, Performance Engineering Senior Site Reliability Engineer, Performance Engineering
Payment Optimization unifies multiple Mastercard capabilities to improve transaction success, reduce avoidable declines, and simplify issuer, acquirer, and merchant interactions across the payment lifecycle. The program centralizes account update orchestration and lifecycle management, leverages AI-driven optimization intelligence, and executes time-critical optimization actions while maintaining clear domain ownership and scalable boundaries.
We build products for scale. The SRE & Performance Engineering team is looking for a strong, innovative engineer to help optimize and scale our suite of services.
This role supports Automatic Billing Updater (ABU), which securely provides participating issuers’ updated cardholder account information—such as account number and expiration date—to ABU-registered merchants. ABU helps reduce preventable card-not-present transaction declines by keeping credential-on-file and recurring payment information current throughout the issuer-cardholder relationship.
In this role, you will apply your experience in API performance testing, automation, scripting, data setup, AI-assisted script generation, bottleneck discovery, performance tuning, and performance data analysis. You will contribute to capacity planning, platform resiliency, and automation practices that improve engineering velocity and operational quality.
Role
• Partner with site reliability engineers and performance engineers to test and tune ABU services before production release through automated test suites, system design consulting, bottleneck analysis, chaos testing, capacity planning, and launch reviews.
• Build, manage, and maintain robust performance testing suites.
• Measure and monitor availability, latency, throughput, performance, and overall system health; communicate test results and recommendations clearly.
• Scale systems sustainably through automation and recommend changes that improve reliability, velocity, and performance.
• Review production incidents, identify contributing factors, and drive solutions that reduce recurrence.
• Manage project priorities, deadlines, and deliverables independently.
• Approach work with an automation mindset and automate repeatable tasks wherever practical.
• Apply deep technical expertise to coach and mentor technical talent.
All About You
• Use AI-assisted engineering tools to accelerate performance test script generation, test data preparation, log analysis, anomaly detection, and repetitive automation while validating outputs through sound engineering review.
• Apply data-driven analysis, observability insights, and automation patterns to identify performance trends, isolate bottlenecks, and recommend measurable improvements to scalability and reliability.
Education (preferred):
Bachelor’s degree in Computer Science, Computer Systems, Information Technology, or a related field, or equivalent practical experience.
Minimum:
• Advanced knowledge of web applications and distributed systems infrastructure.
• Excellent verbal and written communication skills for audiences with varying levels of technical acumen.
• Experience with performance bottleneck analysis and system design for scale.
• Experience with Java Virtual Machine internals and garbage collection tuning.
• Experience with one or more of the following: database internals, server or operating system internals, storage system internals, or performance scaling for related platforms.
• Experience implementing automated performance regression test suites for low-latency, high-throughput financial applications.
• Experience analyzing performance bottlenecks across application code, databases, cache layers, data stores, servers, networks, messaging queues, and streaming platforms.
• Experience analyzing issues holistically, from edge components through application tiers and databases.
• Experience working directly with internal customers, resolving issues and providing performance engineering leadership.
• Working knowledge of AI-assisted development and analysis techniques, including prompt-driven script generation, automation workflow creation, test result summarization, and root cause analysis support.
Preferred:
• Experience with Java, Python, Scala, or other programming and scripting languages.
• Experience with Bitbucket, Maven, Jenkins, Gatling, and BlazeMeter.
• Experience migrating legacy on-premises testing suites to cloud-native stacks.
• Experience migrating performance testing suites from LoadRunner to Gatling or BlazeMeter.
• Strong software performance analysis, bottleneck identification, scaling, and automation experience.
• Experience using AI-enabled tools or large language models to generate, refactor, explain, or optimize performance testing scripts, automation utilities, and troubleshooting workflows.
• Experience applying AI-assisted analysis to performance metrics, logs, traces, dashboards, and incident data to identify patterns, summarize findings, and support faster remediation.
• Familiarity with responsible AI practices, including validation of AI-generated outputs, protection of sensitive data, and alignment with enterprise security and compliance expectations.
Skills/Abilities:
• Displays initiative and ownership.
• Detail-oriented and customer-focused.
• Ability to multi-task and prioritize efforts.
• Ability to learn new technologies quickly and apply them effectively.
• Ability to leverage AI and automation tools responsibly to improve productivity, analysis quality, and consistency while maintaining sound engineering judgment.
• Strong analytical mindset with the ability to translate performance data, AI-assisted insights, and operational signals into clear recommendations.
• Ability to work effectively with team members across multiple geographies.
• Excellent collaboration skills with cross-functional teams.
• Ability to provide positive, professional support to internal and external business partners. 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: $96,000 - $163,000 USD