Location: Barcelona Contract: Indefinido About the Opportunity

We’re looking for a Senior Software Engineer to join Kompanion as the third person in Engineering and one of the first eight employees in the company. You’ll help build the foundations of a robust, AI-native platform for critical tax, accounting, and financial workflows. This is a hands‑on role with broad ownership. You’ll lead features end to end, work closely with Tax, Accounting, Growth, and Operations, and help shape our product, engineering standards, hiring, and technical culture. Our stack and initial architecture are in place. Most of what comes next is still open to influence. How We Build

Our stack includes Java, Spring Boot, Next.js, and PostgreSQL. Engineering owns almost the full product loop: refining problems, researching the domain, writing PRDs, designing solutions, building, shipping, and validating them. We use AI across development and inside the product, from document processing and assistants to autonomous agents. We move fast where we can and carefully where reliability, security, and compliance matter. We avoid unnecessary architecture, excessive meetings, and working from tickets without understanding the problem. What You’ll Be Doing

Owning features end to end, from problem definition to production and validation Building across the stack, with a stronger focus on backend systems and business logic Operating the platform in production and improving its reliability, performance, observability, and security Working closely with Tax, Accounting, Growth,



and Operations Building integrations, automations, internal tools, and AI‑powered features Improving our architecture, developer experience, testing, and engineering standards Reviewing code, mentoring engineers, and participating in hiring What You’ll Need

5+ years of experience building and operating production software Strong backend engineering experience Experience with Java and Spring Boot, or the ability to become productive with them quickly Solid PostgreSQL knowledge, including data modelling and query performance The ability to work with React or Next.js when needed Experience owning systems in production Strong fundamentals in clean code, testing, security, and system design High autonomy and the ability to turn ambiguous problems into shipped products A degree in Computer Science, Software Engineering, or a related field is welcome, but not required. Nice to Have

Experience building regulated, auditable, or high‑stakes software Experience designing a platform from its early stages Experience with security, privacy, or sensitive financial data Experience with event‑driven or asynchronous systems Experience building AI‑powered products or using AI‑assisted development tools Previous early‑stage startup experience Who You Are

You’re a hands‑on, low‑ego engineer who wants to build. You balance speed with rigor, challenge decisions constructively, and seek the source of truth. xiphteb You care about outcomes, communicate clearly, and help others improve.

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📌 Fullstack developer (Barcelona)
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