Senior Back End Engineer

About The Team/Role We are seeking a Senior Engineer in the WEX Mobility Engineering organization. This role will sit in the NAM Experiences team that supports the fleet management and mobility payments solutions to our large customers and partners in North America. Our Mobility systems provide SaaS and API solutions to various customers. WEX Mobility products enable credit issuance to fleet companies and their workers in the form of WEX or cobranded credit cards, usable at fueling stations and select other merchants. At WEX, we provide fleet managers and operators with the flexibility to configure spend controls that restrict fleet members to use their cards at configured merchants, for configured amounts and velocity etc.

How You’ll Make An Impact

• Design, develop, and maintain robust, scalable, and high-performance code in our backend services.
• Develop public REST APIs using Java and internal gRPC APIs for inter-service and inter-system communication.
• Craft systems designs, lead design decisions, and drive alignment with other senior engineers.
• Write automated unit tests, integration tests, end-to-end tests, concurrency tests, load/performance tests.
• Analyze existing systems to identify bottlenecks, tech debt, and implement scalability and stability improvements.
• Implement automation for testing, monitoring, healing, and scaling applications, continuous integration and deployment to reduce time to market
• Collaborate with cross-functional teams, including product managers, designers, and other engineers, to define and implement new features.
• Conduct code reviews (comment, approve, seek revisions, merge), mentor junior and mid-level engineers, and actively promote engineering best practices.
• Dive deep and troubleshoot complex issues, devise fixes, author root cause analysis documents, and ensure lasting performance and reliability.
• Support the objective and comparative analyses of competing technologies to advise the team of pros and cons of a technology solution
• Maintain robust documentation (design docs, run books, change management docs, and readiness plans)
• Provide live-site support for production applications by monitoring systems, ensuring rapid incident resolution, and driving continuous improvement.

Experience You'll Bring

• Bachelor’s degree in Computer Science or Software Engineering
• 5-8 years of professional experience in software engineering.
• Strong understanding of data structures and algorithms, object-oriented design, and problem-solving skills.
• Expertise in designing and developing internet-scale services with scalability, availability, security, and reliability design tenets.
• Professional written and verbal communication skills, and a collaborative and empathetic mindset.
• Prior mentorship of junior engineers.
• Experience with AWS as the foundational cloud infrastructure, encompassing proficiency in its core services, deployment methodologies, observability and monitoring.
• Proficiency in backend development, with proficiency expertise in Java, Go or C#, and associated frameworks like SpringBoot, building and optimizing RESTful APIs, ODATA framework, and SQL/Mongo

Preferred Qualifications

• Master’s degree in computer science or software engineering.
• 8+ years of experience in software engineering.
• Experience with event-driven architecture and tools like Kafka.
• Experience working on payment solutions.
• Familiarity with cloud-native architecture (containerization using tools such as Docker and Kubernetes).
• Extensive API security and PCI DSS compliance exposure.
• Ability to work on existing codebase, contribute improvements, and transition legacy systems to modern technologies.