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Agent guide: [/agents.md](https://www.wearedevelopers.com/agents.md). --- # Staff Software Engineer - **Company:** WEX Inc. - **Location:** United States (Remote available) - **Experience:** Expert - **Salary:** $140,600 - $173,100 - **Contract:** Permanent contract - **Skills:** Clean Code Principles, Java (Programming Language), A/B Testing, Application Programming Interfaces (APIs), Artificial Intelligence, Amazon Web Services, Application Lifecycle Management, Business Logic, Cloud Engineering, Code Generation, Continuous Integration, Cursor, Drools, JSON, RabbitMQ, Microsoft Copilot, Swagger, Salesforce.Com, Software Engineering, Openapi, Dynamic Routing, Spring Cloud, GitHub Copilot, Large Language Models, Spring-boot, AI Coding Agents, Backend, Event Driven Architecture, Information Technology, Apache Kafka, Front End Software Development, Api Design, Data Pipelines, Api Management, Legacy Systems, Microservices - **Published:** November 7, 2026 - **Apply:** https://startup.jobs/staff-engineer-wex-europe-limited-10709481 ## About the Role * 10+ Years of Engineering Excellence: Proven track record in backend architecture, specifically within Fintech, Lending, or Credit systems. * Modern Java Stack: Expert-level proficiency in Java 17/21, Spring Boot 3.x, and Spring Cloud. * Monolith-to-Distributed Migration: Significant experience extracting tightly coupled business logic from legacy backends into external, scalable cloud microservices (AWS). * Complex Adjudication & Rules Engines: Experience building or implementing rules engines (e.g., Drools, Camunda, or custom JSON-logic) for automated decisioning. * Event-Driven Design: Deep experience with Kafka or RabbitMQ for maintaining asynchronous data consistency between the new API layer and legacy systems of record during migration phases. * Contract-First Development: Strict adherence to API contracts (OpenAPI/Swagger) to ensure seamless collaboration with frontend teams. AI & Modern Delivery Tools: * AI DLC Proficiency: Hands-on experience using AI coding assistants (Cursor, Copilot, etc.) to optimize workflows, refactor legacy code, and accelerate delivery. Leadership & Education: * Strong analytical skills and a proven capability in resolving complex, cross-functional problems. * Excellent written and verbal communication skills; ability to present complex technical concepts clearly to stakeholders. * Bachelor's degree in Computer Science or a related technical field. ## Description As a Staff Software Engineer, you will be the primary architect and execution lead for leading the platform changes for the Digital Credit Application. We are pivoting from a legacy monolith to a high-performance, pluggable API ecosystem. Your mission is to decouple core adjudication logic, enable rapid A/B testing of the customer journey, and lay the technical foundation for future AI-driven chat and automated decisioning experiences. This is a high-impact role designed for a true "builder" who thrives on the duality of supporting a live production environment while aggressively migrating mission-critical services to a modern, microservices-based backbone. You will encounter varied customer scenarios where your out-of-the-box approach is a better fit than standard industry practices. We expect you to make a true difference for the customer, leveraging technology and AI to best serve and solve for good. The AI Edge: We are a forward-thinking engineering org. You are expected to be an expert in leveraging AI Software Development Lifecycle (ADLC) tools (e.g., GitHub Copilot, Cursor, Amazon Q, LLM-based code gen and architecture agents) to accelerate migration, write bulletproof tests, and automate documentation. How you'll make an impact: Architectural Migration & Strategy: * Strangler Fig Migration: Lead the decoupling of core credit application logic out of the legacy monolith and into a scalable, cloud-native Java/Spring Boot micro services environment. * Migration with Zero Downtime: Design and execute high-volume traffic migration strategies from legacy systems to new stacks seamlessly without disrupting live customers. * Salesforce Proficiency: A significant portion of existing systems is embedded within various Salesforce capabilities throughout the application lifecycle. Proficiency in Salesforce is a strong advantage, as different integrations will require the new stack to support bidirectional data and state synchronization within the Salesforce ecosystem. Pluggable Adjudication & API Ecosystem: * Modular Architecture: Design and implement a modular adjudication layer allowing the business to swap or update credit rules and third-party data providers without impacting core application flows. * API-First Design: Build and maintain robust, versioned REST/gRPC APIs that support a multi-channel experience (Mobile, Web, and future AI Chat interfaces). * A/B Strategy Enablement: Engineer backend infrastructure for dynamic routing and experimentation, allowing real-time testing of various application flows. AI Readiness & Process Acceleration: * AI DLC Mastery: Champion the use of AI tools across the development lifecycle to write code faster, refactor legacy code into modern Java, and generate robust test suites. * Data Science Partnership: Partner with Data Science teams to ensure data pipelines and backend schemas are optimized for LLM integration and real-time credit decisioning models. Operational Excellence & Leadership: * Observability & CI/CD: Establish rigorous standards for CI/CD, observability (OpenTelemetry), and automated contract testing. * Technical Mentorship: Provide guidance to mid-level and senior engineers, fostering a culture of high engineering standards, clean code, and AI-assisted productivity.