Backend Engineer (AI, API)

About The Company WEX is a global leader in innovative payment solutions, providing a broad spectrum of financial technology services that enable businesses to manage their spending, optimize operations, and enhance financial efficiency. With a focus on delivering scalable and secure payment platforms, WEX serves diverse industries including fleet management, healthcare, travel, and corporate payments. The company is committed to leveraging cutting-edge technology to create intelligent, proactive solutions that meet the evolving needs of its clients worldwide. WEX's dedication to innovation, security, and customer-centricity has established it as a trusted partner in the fintech ecosystem, driving growth and operational excellence across multiple sectors. About The Role We are seeking a seasoned Staff Software Engineer to join our North America Mobility organization remotely, with residency within 30 miles of Boston, MA San Francisco Bay Area, CADallas, TXSalt Lake City, UTSeattle, WA; or Portland, ME. This pivotal role will be part of the Platform team, focusing on building an advanced AI Platform to accelerate feature development and deliver intelligent solutions. The successful candidate will contribute to the architecture, development, and deployment of autonomous AI agents, skills, MCP servers, and AI tools designed for sophisticated reasoning, strategic planning, and complex workflow orchestration. Operating at the forefront of generative AI, distributed systems, and fintech, this role offers a unique opportunity to influence the future of AI-driven financial services, empowering WEX to provide proactive, highly intelligent solutions to a global user base. The Platform team is dedicated to creating scalable, reliable, and maintainable UI and API solutions that enable internal teams to innovate rapidly. Within the NAM Mobility ecosystem, our products facilitate strategic credit issuance to fleet organizations, offering features such as fuel discounts, spend controls, and transaction management. This role involves designing and implementing high-performance backend services, developing AI systems, and ensuring seamless integration across various platforms, all while maintaining high standards of security, stability, and scalability. Qualifications Bachelor's degree in Computer Science, Software Engineering, or related field 8-10 years of professional experience in software engineering Strong understanding of data structures, algorithms, and object-oriented design Expertise in designing and developing scalable, secure, and reliable internet-scale services Proficiency in backend development with Java or C#, including frameworks like SpringBoot Experience building and optimizing RESTful APIs, SQL, and related technologies Hands-on experience with AI/LLM-powered applications, agent-based systems, or related AI frameworks Familiarity with MCP protocols or similar frameworks for system integration Experience with prompt engineering, embeddings, vector-based retrieval, and AI safety practices Excellent communication skills and a collaborative mindset Responsibilities Design, develop, and maintain high-performance backend services using object-oriented programming Create and optimize public REST APIs and internal gRPC APIs for system communication Lead system design discussions, make architectural decisions, and align with engineering standards Write comprehensive automated tests, including unit, integration, and performance tests Analyze existing systems to identify bottlenecks, tech debt, and implement scalability improvements Implement automation for testing, monitoring, healing, and scaling applications Participate in continuous integration and deployment pipelines to accelerate delivery Collaborate with cross-functional teams to define and develop new features and enhancements Conduct code reviews, mentor junior engineers, and promote best engineering practices Investigate and resolve complex production issues, perform root cause analysis, and ensure system reliability Maintain detailed documentation including design documents, run books, and change management records Provide live-site support, monitor system health, and drive incident resolution Lead cross-team projects as a technical owner or team lead, facilitating progress and removing blockers Design and build agentic AI systems, enabling autonomous workflows, reasoning, and multi-step decision-making Develop and scale multi-agent architectures, integrating AI with enterprise data and APIs using MCP or similar protocols Build and optimize LLM-powered services, ens