Senior Go Engineer (Payment Gateway Solutions)

Location: Warsaw, Poland; Belgrade, Serbia; Limassol, Cyprus; Yerevan, Armenia; Barcelona, Spain Join COLIBRIX ONE – Innovating the Future of Payments At COLIBRIX ONE*, we're building advanced, AI-powered payment technologies that support Payment Service Providers (PSPs), Electronic Money Institutions (EMIs), and neobanks across the EU and the UK. As a fully licensed Electronic Money Institution (FCA Reference No. 927920) and holder of a Financial Institution Licence issued by the MFSA, as well as a principal member of both VISA and Mastercard, we provide comprehensive, real-world financial solutions that include: Global card processing Digital wallet infrastructure Cross-border merchant accounts Alternative payment methods (APMs) Corporate accounts for legal entities We're a fast-growing team with a passion for innovation, security, and scalability. Our culture values curiosity, collaboration, and impact - and we're looking for talented professionals who are ready to shape the future of fintech. At COLIBRIX ONE, your work directly powers the digital economy. If you're eager to solve meaningful challenges and build with purpose, we'd love to hear from you. We're seeking an experienced Go Engineer to join our team and contribute significantly to our payment gateway product. The ideal candidate will bring deep technical expertise, a collaborative mindset, and the ability to influence and mentor team members through knowledge and experience rather than formal authority. About the project: Payment gateway solutions - fintech product that securely connects merchants and financial institutions to process online payments in real time. It handles transaction routing, encryption and tokenization, fraud and risk checks, and integration with acquirers, payment aggregators and alternative payment methods. The Payment Gateway supports high availability, scalability, and compliance with PCI DSS and PSD2. Tech stack: Go, PostgreSQL/MySQL, MongoDB/Redis, Kafka, NATS, REST/gRPC, AWS, GitLab CI/CD, Prometheus, Grafana. Key responsibilities: Design and develop Go-based services for the payment gateway and related fintech systems, focusing on stability, fault tolerance, and correct handling of financial operations Translate business requirements into clear technical specifications and propose concrete solutions at the service and module level, including API design, data models, and integrations with external providers Build solutions in compliance with security requirements, including PCI DSS, proper handling of sensitive data, and secure inter-service communication Analyze and optimize service performance, including code profiling, concurrency handling, and efficiency of data storage and network interactions Participate in the architecture of microservices: service boundaries, communication patterns, load balancing, error handling, queues/streaming, and data storage approaches Produce maintainable, testable code with appropriate unit and integration test coverage, following team development standards Participate in code review as part of the development process: evaluate implementations, identify issues, and provide constructive feedback aligned with technical requirements Contribute to technical discussions by offering concrete, practical solutions within the current architecture and development processes What You Need to Succeed in This Role: 3–5 years of Go development experience focused on backend systems, and around 5 years of experience working with fintech applications Understanding of distributed systems, microservices architecture, and API design, including REST/RPC transports Experience working with SQL and NoSQL databases, message brokers (Kafka, NATS), and caching systems Familiarity with CI/CD practices and tools, preferably GitLab Experience working with the AWS cloud platform Ability to contribute expertise and collaborate with the team on technical solutions Strong communication skills and the ability to explain complex technical ideas to colleagues with varying levels of technical background Fluency in written and spoken English and Russian Experience in the fintech domain Security-by-design mindset: ability to design solutions with security considerations built in at every stage Understanding of regulatory requirements in the fintech space (e.g., PCI DSS, GDPR) Experience in performance optimization and building high-availability systems Experience with observability tools: logging, metrics, tracing (Prometheus, Grafana, OpenTelemetry) Experience integrating with external payment providers, processors, or anti-fraud systems What We Offer: Opportunity to shape the future of fintech solutions within a growing company Collaborative, horizontal team structure that values your expertise and ideas Continuous learning and development opportunities to enhance your skills and career growth Competitive salary and benefits package Flexible work arrangements to support work-life balance * This position is offered within the COLIBRIX ONE. Employment will be under the appropriate legal entity based on the role and location.