Backend Engineer (m/f/d) - Kotlin / Java

Academic Key; Berlin; Hybrid; EUR 70,000 - 98,000; Full time

Benefits offered by this job

Hybrid work model

Centrally located office in Berlin

Dog-friendly office

30 vacation days

Employee discounts

Job summary

rebuy in Berlin is seeking a Backend Engineer (m/f/d) with Kotlin/Java experience to help scale our AI-powered marketplace platform. You will write clean, testable code, review peers, and help evolve the architecture while delivering solid solutions across services.

Join a small, collaborative team in Berlin Hybrid mode, with a transparent culture, flexible work environment, and benefits including a centrally located office, 30 vacation days, dog-friendly policy, and employee discounts.

Qualifications

• 2+ years professional software development experience in Kotlin or Java.
• Hands-on experience using AI coding tools in daily work.
• Strong CS fundamentals in algorithms and data structures.
• Relational database experience with Postgres.
• Familiarity with CI/CD pipelines and Maven.

Responsibilities

• Write clean, readable, testable code and contribute with AI-assisted development.
• Conduct code reviews and provide constructive feedback.
• Collaborate across teams to evolve architecture and reduce technical debt.
• Take ownership of projects and deliver end-to-end solutions.
• Maintain and extend existing services while building new ones.

Skills

Kotlin/Java experience

AI tooling usage

CS fundamentals

Tools

Postgres

Maven

Job description

# Backend Engineer (m/f/d) - Kotlin / Java**rebuy** · Berlin, Berlin, GermanyAbroad Berlin, Berlin, Germany◷ Experienced fulltime permanent✓ Link validatedReady to become part of the most important mission on this planet? We are rebuy, pioneers in the sustainable reuse of electronics and media, and we are looking for you! Our mission: to make circular living accessible to all, one transaction at a time. By giving products a second chance, we reduce resource consumption and avoid unnecessary e-waste. Our global team of 500 drives things forward collaboratively, takes personal responsibility, values constructive critical thinking, and is dedicated to serving our customers and planet. The Role We are looking for a passionate and experienced Software Engineer who loves working in a team and has a strong getting-things-done attitude. You will be part of a small but fun team of 4 people working on some of the most business-critical and technically interesting parts of rebuy's platform. Our scope covers AI-powered customer support automation, payment systems, and marketplace integrations (Amazon, eBay). We build on a modern, actively evolving stack, and we expect everyone on the team to use AI tools as a natural part of their workflow. Key Responsibilities: Write code that is simple, readable, testable, and maintainable, whether you write it yourself or with the help of AI tools Conduct code reviews, give helpful feedback, actively contribute in team discussions and decisions Know the sweet spot between implementing beautiful and charming solutions which incorporate all existing software design patterns and just getting it done Suggest changes to our software that simplify the technical architecture of individual services or pay down technical debt Actively take over ownership for projects and collaborate with different teams across the organization Maintain existing services and contribute to developing the new solutions Requirements: 2+ years of professional software development experience in Kotlin or Java (mandatory) Hands-on experience using AI coding tools (e.g. Claude Code, Cursor, etc.) in your daily work, and a clear sense of where they help and where human judgment matters most Strong Computer Science fundamentals in algorithm design, data structures, problem-solving, and complexity analysis; these matter even more when you're reviewing and steering AI output Knowledge and experience with database design Extensive experience with relational databases, including Postgres You are not dependent on libraries (or AI tools), but know when, where, and why you should use them Familiarity with CI/CD pipelines and comfort with build automation and dependency management tools like Maven A collaborative mindset and experience working across teams and functions Curiosity, openness to learning, and the confidence to step outside your comfort zone Clear and direct communication Location: Berlin Hybrid model Purpose, a great company culture and incredible benefits - what to expect at rebuy: Work with a friendly team that is passionate about circularity and wants to make the world a little more sustainable, one transaction at a time. Feel comfortable in an environment where independence and new ideas are welcome. Benefit from flat hierarchies and the greatest possible transparency so that things don't take longer than they have to and you always feel well informed. Enjoy our centrally located office in Berlin (Erkelenzdamm 11 - 13, 10999 Berlin). Benefit from our family-friendly, flexible environment and paid child sick leave. Bring your dog to the office: we love animals and want to cuddle yours, too! Use employee discounts on rebuy.de , sustainable products at Futurebens , offers for sustainable micro-mobility and massages directly in our office. Have fun at our legendary team and company events. Use our mental health offers as part of a cooperation with Nilo . Take care of your work-life balance with 30 vacation days. Stay active with our own gym located directly in the building, making it easy to fit workouts into your daily routine. Benefit from an on-site daycare in the building, supporting a truly family friendly and flexible working environment. \\*At rebuy all people are welcome and supported! We would like to talk, regardless of age, disability, national and social origin, skin color, religion, gender identity and sexual orientation. Just be who you are. Find Jobs in Germany on Arbeitnow