Senior Software Engineer; Golang

We are expanding our Tech team with a Senior Software Engineer based onsite inour office in Barcelona!

As a Senior Software Engineer, you will design, build, and operate the backend systems that power Fast Track’s platform. Our infrastructure runs on AWS, orchestrated with Kubernetes (EKS) and Docker, and leverages services such as, and Cloudflare for edge delivery and serverless workloads. Data is managed across MySQL, Amazon RDS Aurora, Click House for analytics, and in-memory stores, including Amazon Elasti Cache and Memory

DB. Observability is driven by Prometheus and Grafana, with Open Telemetry being assessed as a future standard.

To be successful in the role, you will need a strong product mindset and enjoy working closely with real customers, and care deeply about building systems that last.

• Design and develop backend services and APIs that power the Fast Track platform
• Build scalable, reusable frameworks and shared libraries that accelerate delivery across teams
• Refactor existing solutions to reduce duplication, fragility, and operational overhead
• Contribute to improving observability (logging, metrics, alerts), so issues surface early

• Treat integrations as part of the product, not just technical glue
• Understand partner use cases and constraints with support from senior engineers
• Help balance short-term delivery with longer-term maintainability
• Ask “why” and propose improvements when current solutions don’t scale

• Write testable, maintainable code with appropriate unit and integration tests
• Ensure features are production-ready before handoff, meeting quality, security, and reliability standards.
• Lead incident response within the owned domain, drive root cause analysis, and embed systemic improvements into engineering practices
• Keep documentation for owned systems accurate and up to date

• Collaborate closely with Product, Tech Leads, and peers
• Actively participate in code reviews and design discussions
• Learn and apply best practices in system design, performance, and reliability

• Be curious and proactive about how emerging technologies can improve productivity, code quality, and decision-making
• Use emerging technologies as a multiplier: faster exploration, better debugging, clearer documentation
• Focus your human effort on what matters most: system design, product thinking, trade-offs, and ownership
• Stay grounded: understanding where emerging technologies help and where engineering judgment still matters most

• Extensive experience in backend development, working with complex production-grade systems
• Proven ability to design, build, and evolve high-performance microservices in high-traffic environments
• Strong experience designing scalable APIs and distributed systems, with clear separation of concerns
• Demonstrated expertise in building testable, high-quality code, including unit, integration, and load testing
• Strong understanding of systemic code and architecture quality, with the ability to identify and resolve cross-area issues
• Proven experience establishing and driving testing best practices, automation, and a continuous testing culture
• Ability to lead and review complex pull requests, providing forward-looking architectural feedback and mentoring other engineers
• Experience in defining and enforcing coding guidelines and quality standards, raising the bar across the team
• Strong system design skills, including leading design discussions, articulating trade-offs, and making sound technical decisions under constraints
• Ability to balance short-term delivery with long-term architectural health, breaking down large initiatives into incremental deliverables
• Experience in anticipating technical and delivery risks and defining mitigation strategies
• Hands‑on experience contributing to or leading incident response, ensuring learnings are embedded into engineering and delivery practices
• Strong collaboration skills, including working closely with Product and UX to prioritise and validate early…