Senior Software Engineer

Our Purpose Mastercard powers economies and empowers people in 200+ countries and territories worldwide. Together with our customers, we’re helping build a sustainable economy where everyone can prosper. We support a wide range of digital payments choices, making transactions secure, simple, smart and accessible. Our technology and innovation, partnerships and networks combine to deliver a unique set of products and services that help people, businesses and governments realize their greatest potential. Title and Summary Senior Software Engineer Senior Software Engineer, Blockchain Team Location: Lisbon, Portugal Experience: 5+ years Employment Type: Full-time Overview We are seeking a highly skilled Senior Software Engineer to join our Blockchain Team in Lisbon. In this role, you will design, develop, and maintain secure, scalable, and high-performance distributed systems that support blockchain-based products and services. You will collaborate with cross-functional teams to deliver innovative solutions while driving engineering excellence and mentoring other developers. Key Responsibilities • Design, develop, and maintain blockchain platforms and distributed applications. • Build secure and scalable backend services using modern software engineering practices. • Develop integrations with blockchain networks, digital asset platforms, and cryptographic services. • Create and maintain APIs, microservices, and cloud-native applications. • Participate in architecture discussions and influence technical direction. • Ensure high availability, performance, security, and reliability of production systems. • Experience with cryptographic protocols, key management, and secure data handling practices. • Conduct code reviews and mentor junior and mid-level engineers. • Collaborate with Product Managers, Architects, Security Engineers, and Operations teams. • Drive automation, testing, CI/CD, and operational excellence initiatives. • Troubleshoot complex technical issues across distributed environments. Required Qualifications • Bachelor's or Master's degree in Computer Science, Software Engineering, or a related field. • 5+ years of professional software engineering experience. • Strong proficiency in Java and Spring. • Experience developing full-stack applications, including scalable backend services and modern, responsive frontend solutions. • Strong hands-on experience with frontend framework Angular. • Experience building responsive, accessible, and user-friendly web applications. • Strong understanding of REST APIs, GraphQL, and frontend-backend integration patterns. • Experience building scalable microservices and distributed systems. • Strong understanding of cloud platforms such as AWS or Azure. • Solid knowledge of software design patterns, system architecture, and performance optimization. • Experience with CI/CD pipelines, containerization, Docker, and Kubernetes. • Familiarity with modern testing frameworks for both frontend and backend development. • Excellent problem-solving, communication, and collaboration skills. • Ability to lead technical initiatives, mentor engineers, and drive best practices across the software development lifecycle. Preferred Qualifications • Experience with blockchain technologies such as Ethereum, Hyperledger, Bitcoin, Polygon, Solana, or similar platforms. • Understanding of cryptography, PKI, digital signatures, encryption, and secure key management. • Experience developing user interfaces for blockchain or digital asset platforms. • Knowledge of Web3 technologies, wallet integrations, and smart contract interactions. • Experience with event-driven architectures, messaging systems, and real-time applications. • Experience designing and implementing secure authentication and authorization solutions (OAuth2, OIDC, MFA). • Previous experience leading technical projects and mentoring engineers. What Success Looks Like • Delivering reliable and secure blockchain solutions to production. • Improving system scalability, maintainability, and performance. • Influencing architectural decisions and engineering standards. • Supporting team growth through technical leadership and mentorship. • Driving innovation in blockchain, security, and distributed systems technologies. Key Competencies • Technical Leadership • Distributed Systems Design • Blockchain Architecture • Secure Software Development • Cloud-Native Engineering • Problem Solving • Collaboration and Communication • Mentorship and Coaching Corporate Security Responsibility All activities involving access to Mastercard assets, information, and networks comes with an inherent risk to the organization and, therefore, it is expected that every person working for, or on behalf of, Mastercard is responsible for information security and must: Abide by Mastercard’s security policies and practices; Ensure the confidentiality and integrity of the information being accessed; Report any suspected information security violation or breach, and Complete all periodic mandatory security trainings in accordance with Mastercard’s guidelines.