Senior Developer (High Throughput APIs)

Emagine is seeking a Senior Developer (High Throughput APIs) to join a collaborative engineering team within the Payments / Fintech sector. This is an opportunity for an experienced Backend Developer to contribute to the development and evolution of a core financial processing platform, ensuring high performance, scalability, reliability, and security across backend services and APIs. What You'll Be Working On Design and develop highly scalable backend services and B2B APIs. Build and maintain systems capable of handling very high transaction volumes. Take ownership of complex technical challenges from design through to production. Design APIs, services, data models, and distributed systems with scalability and reliability in mind. Develop clean, maintainable, testable, and production-ready code. Work extensively with relational databases and SQL, including query optimization and indexing. Identify and resolve performance bottlenecks across applications, databases, and systems. Design asynchronous processing and concurrent workloads. Contribute to the migration and modernization of existing PHP and Java modules towards Go. Design resilient systems with appropriate retry, recovery, and dead-letter mechanisms. Implement observability through structured logging, metrics, tracing, and production monitoring. Apply security principles throughout API and service design and implementation. Contribute to automated testing, CI/CD, containerization, and production deployments. Review code and technical designs, providing meaningful feedback to other developers. What We're Looking For Strong proficiency in PHP and Java. Experience designing and developing backend systems. Strong understanding of relational databases and SQL optimization. Experience working with high-transaction-volume systems. Familiarity with asynchronous processing and concurrent workloads. Ability to contribute to system design, architecture, and security. Strong problem-solving skills and a focus on performance, scalability, and reliability. Professional fluency in English. Fluency in French is a plus. Nice to Have Experience with Go. Knowledge of AWS services. Familiarity with observability tools such as Grafana, Loki, and Alloy. Experience with PostgreSQL. Familiarity with Agile methodologies. Experience in Payments, Fintech, or other financial processing environments. Experience modernizing legacy systems and migrating services towards modern architectures. Location & Eligibility Candidates must be based in Portugal. Remote working model. Duration: 6-12 months. About emagine At emagine, we value diversity, inclusion, and equal opportunities. We believe that different perspectives drive innovation and create stronger teams, and we are committed to fostering an inclusive environment where everyone can thrive. We work with leading international clients on innovative and high-impact projects, offering opportunities to grow both professionally and personally. If you are interested in this opportunity, we encourage you to apply and become part of a dynamic and forward-thinking environment. To learn more about us, visit our website: