Payment Software Engineer Jobs in Chicago, IL (NOW HIRING)

Kunai builds full‑stack technology solutions for banks, credit and payment networks, infrastructure providers, and their customers. Together, we are changing the world's relationship with financial services. At Kunai, we help our clients modernize, capitalize on emerging trends, and evolve their business for the coming decades by remaining tech‑agnostic and human‑centered.

We are seeking a Senior Software Engineer to join a high‑impact digital payments modernization program supporting the integration of a major card network into one of the largest financial institutions in the United States. This is a hands‑on engineering role at the intersection of legacy and modern infrastructure, where you will contribute to both the reliability of mission‑critical payment systems today and help shape the architecture that will power them tomorrow. You will work across scalable backend services, performance testing frameworks, and application engineering – with real opportunity to grow your skills on modern cloud‑native technologies as the program evolves.

• Design and execute enterprise‑grade performance testing strategies for payment processing services, defining frameworks, tooling, and success criteria from the ground up.
• Identify performance bottlenecks across legacy and modern service layers and drive measurable improvements through analysis and targeted optimization.
• Instrument and validate services running on Java, Oracle, Tomcat, and WebSphere as well as modern workloads running on PostgreSQL and OpenShift.
• Collaborate with backend engineers to ensure scalability requirements are met across all environments prior to release.
• Translate performance findings into clear recommendations for engineering leads and stakeholders.

• Build and maintain full‑stack backend services supporting card network integration, working primarily in Java with PostgreSQL and OpenShift Container Platform (OCP).
• Contribute to application modernization efforts, migrating and re‑platforming services from legacy infrastructure to cloud‑native environments.
• Leverage AI‑assisted development tooling (including GitHub Copilot) to improve development velocity and code quality.
• Participate in code reviews, architectural discussions, and cross‑team technical planning sessions.

• PCI data purging pipelines and event‑driven architecture patterns including token removal and event consumption.
• Work with event‑driven services running on OpenShift, Oracle and PostgreSQL backends to support data lifecycle and compliance requirements.
• Serve as a flexible, senior contributor across teams where engineering depth and experience are needed most.

• 5+ years of professional software engineering experience, primarily in Java.
• Strong working knowledge of relational databases – Oracle and/or PostgreSQL required.
• Experience deploying and operating services in containerized environments (OpenShift, Kubernetes, or equivalent).
• Familiarity with legacy enterprise application servers – Tomcat and/or WebSphere experience a plus.

• At least one enterprise‑level performance testing engagement – defining strategy, selecting tooling, executing tests, and presenting findings.
• Experience with performance profiling, load testing, and bottleneck resolution in high‑throughput, distributed systems.
• Ability to design logical, streamlined test frameworks from scratch and operate with minimal guidance.

• Background in digital payments, card processing, or financial services technology strongly preferred.
• Understanding of PCI compliance requirements and secure data handling practices.
• Familiarity with event‑driven architecture patterns and OpenShift‑based eventing.

• Demonstrated ability to work effectively in large, matrixed program environments with multiple teams and stakeholders.
• Strong written and verbal communication skills; able to translate technical complexity for non‑technical audiences.
• Comfortable operating in environments with evolving requirements and ambiguity.

• Experience with PGLogical or PostgreSQL logical replication.
• Exposure to AI‑assisted development tools (GitHub Copilot or Claude).
• Prior work on bank or card network integration programs.
• Experience working in segregated or air‑gapped development environments.

We are proud to offer our employees a range of benefits, including competitive compensation, professional development opportunities, and flexible work arrangements, all designed to help them thrive.