C1: GPN - Java Engineers for ARP/ETB Integration

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. Some things you may work on You will be embedded across one or more workstreams supporting digital payments engineering, with responsibilities that may include: Domain & Service Architecture - Apply domain-driven design to define bounded contexts, domain models, and aggregate boundaries for card-network reference data — establishing a ubiquitous language shared across engineering and business stakeholders. - Develop and harden a Spring Boot / JPA / PostgreSQL Aurora service with Liquibase-managed schema migrations, a Drools-based business rules engine, and scheduled batch jobs — including designing authorization and data-access controls from the ground up where none exist today. - Design and own integration workflows and routing using Apache Camel (or equivalent), orchestrating multi-step, stateful operations such as request intake, validation, approval, and publication pipelines. - Develop an event-driven backbone using Kafka — topic/schema design, producer/consumer reliability patterns, and integration with the rules engine and workflow layer. Frontend & Identity - Develop a micro-frontend application (Next. js/React/TypeScript) as an independently deployable system, and design its convergence path into the card network's future shared micro-frontend shell. - Own the OAuth2/OIDC identity architecture end-to-end — provider integration (Okta), JWT/token validation strategy, session/revocation design, and trust-boundary decisions across environments.

Cloud & Platform - Design and govern AWS IAM policy, S3, and CloudFront architecture across multiple environments — this is not config-following; you're expected to set the standard. - Lead deployment on the organization's internal static cloud hosting platform. - Drive test-driven development practice across the team and build out continuous testing/automation pipelines (unit, contract, integration, and end-to-end) as part of CI/CD. Scalability, Performance Testing & Validation - 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. Application Engineering - 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.