Senior Java/Kotlin Developer

🪐 Discover our galaxy Join the Future of Work ! Keystone AI is Europe's leading freelance marketplace, connecting over 1,000,000 talented freelancers with 100,000+ companies. Founded in 2013, we're transforming how work gets done through our tech-powered, human-centered platform. What makes us different: - A diverse team of 600 Keystone AI ers across 6 European countries - A culture that champions equality (50% of our Comex are women) and inclusive growth - Backed by top investors including ISAI, Serena Capital, Eurazeo Growth, Goldman Sachs, and BPI - A mission to give everyone the freedom to work differently Ready to help shape the future of work? Your next chapter starts here! 🪐 Key responsibilities ✨ Collaborative Product Leadership: You'll establish a strong partnership with Product Managers and Designers to translate user needs into innovative technical reality. You thrive in the creative process, confidently challenging ideas and co-creating elegant solutions that directly solve end-users problems. Take the lead : You’ll own your features end-to-end. From first sketch to release (and beyond). You’re empowered to make decisions and trusted to do what’s right for the product. Build smart, ship fast : We deploy to production around 70 times a week. You’ll help us keep that rhythm by balancing speed, quality, and business impact. Be a partner : You bring strong opinions, backed by experience, and you’re not afraid to challenge the status quo when it makes sense. AI-Augmented Craft: You are curious about (or already using) tools like Cursor, Gemini or Claude Code . You see AI as a pair-programming partner that accelerates delivery while you maintain the "human-in-the-loop" for quality and strategy. Knowledge Multiplier: As a senior, you’ll help the team navigate this new AI landscape. You’ll share best practices on prompt engineering, AI-driven refactoring, and maintaining a high "quality bar" in an automated world. Our Tech Stack Frontend : TypeScript, Vue.js, Nuxt, Internal Design System , Stencil.js Backend: Kotlin, Java Spring Boot, Gradle, PostgreSQL, MongoDB, Elasticsearch, RabbitMQ, Redis Platform : Google Cloud Platform, Kubernetes, Terraform, ArgoCD, Gitlab CI The AI Toolkit : We empower our devs with modern AI coding assistants and are building internal workflows and investigating as many uses as possible (docs, unit tests, migrations) Data : BigQuery, dbt, Looker, Spark, Python Life @ Keystone AI Remote Culture: Strong remote culture with most of the team working full-remote from countries where Keystone AI has a physical office and legal entity (France, Germany, Spain, Belgium, Netherlands, or UK). Tech Days: 15% of engineering time dedicated to technical project, , continuous training and learning, R&D and technology watch. Tech Conferences: Annual Product, Tech and Data workshop, annual Keystone AI Tech Days, organized and presented by Keystone AI ’s engineering team. Opportunity to attend major tech conferences. About you 🧑‍🚀 Bring 6+ years of professional software development experience, including a first role within a product company (SaaS, fintech, marketplace, etc.) Demonstrate deep proficiency in Java or Kotlin , with confidence in navigating complex backend architectures, APIs, and data models. Product-First Champion : You think beyond the code, driven by curiosity about the user's "why." You proactively propose improvements and champion end-to-end feature ownership from conception to delivery. Pragmatic Architect : You drive architectural decisions, leveraging patterns like Hexagonal Architecture for modularity and testing. You skillfully balance long-term scalability with the need to iterate quickly AI Empowerment : You view AI as an accelerating force, effectively delegating routine tasks to tools while remaining the strategic "Pilot" responsible for quality, integrity, and preventing architectural drift. Full Lifecycle Stewardship : You maintain stewardship over the entire feature lifecycle. From building CI/CD and testing to ensuring observability and monitoring. Shipping is just the start; you are dedicated to quality, longevity, and scalable performance. Fluent in English , you are comfortable speaking and writing in an English-speaking environment. How to join the mission? 🚀 Screening with Alex , our Talent Acquisition Manager, to better understand your background, aspirations and answer your questions (45 minutes) Interview with one of our Engineering Manager, to discuss your experience and the role in more detail (75 minutes) Technical assignment (homecase or livecase, you choose) to prepare and present in order to evaluate your hard skills (90 minutes) Final interview with Jean (VP Engineering) to discuss Keystone AI ’s long term vision (45 minutes) We will send you an interview guide so you can best prepare yourself. Keystone AI is the perfect space to thrive personally and professionally 💫 - Onboarding: Before easing into your new role, you’ll spend your first week learning about our culture, products, and services with