N-iX is a global software development service company that helps businesses across the globe create next-generation software products. Founded in 2002, we unite 2,400+ tech-savvy professionals across 40+ countries, working on impactful projects for industry leaders and Fortune 500 companies. Our expertise spans cloud, data, AI/ML, embedded software, IoT, and more, driving digital transformation across finance, manufacturing, telecom, healthcare, and other industries.

Our client is a fast-growing European fintech company in the business spend management space — corporate cards and related financial products — serving SME and mid-sized business customers across the EU and UK, in a regulated environment with GDPR compliance obligations. Engineering is organized into cross-functional squads, with platform/enabling teams providing shared tooling horizontally. The client already runs an AI-native engineering practice: Claude Code and GitHub Copilot are used daily, supported by a growing library of shared, versioned Skills embedded in key repositories, enabling an end-to-end flow from ticket to implementation, testing and PR in several codebases.

The client is AWS-first overall; for data platform and analytics workloads it also runs GCP,



with BigQuery as the primary data warehouse. Day-to-day coordination is Slack-first, with Linear for ticket tracking, GitHub for code/PR review, and Notion as the knowledge base. We're looking for a Senior Full-Stack Engineer working across the Kotlin backend and React/TypeScript frontend, with a clear leaning toward either front-end or back-end depth and the ability to move fluidly between layers to unblock delivery.

Deliver across the Kotlin backend and React/TypeScript frontend Multiply the output and quality of the squad you join, and share patterns/practice beyond your immediate team so adoption compounds across the organisation Kotlin (backend) and React/TypeScript (frontend) A clear leaning toward front-end or back-end depth, with the ability to move fluidly across stack layers Experience with AWS Agent & harness engineering fluency, with concrete evidence of building/operating this kind of tooling, not just using it. PostgreSQL Flexible working format - remote, office-based or versátil Professional development tools (mentorship program, tech talks and trainings, centers of excellence, and more) not applicable for freelancers

📌 Senior Full-Stack Engineer (with AI agents experience) (Madrid)
🏢 N-iX
📍 Madrid