Senior Fullstack Software Engineer in Berlin

• In this role, you’ll drive growth through experimentation. You’ll turn ideas into hypotheses, ship experiments fast, read the results, and build more of what works for our users and our business. You’ll own features end to end, from the backend to the user interface
• Our newer frontends run on React.js, Next.js and TypeScript, wired to our platform through GraphQL and Apollo Client, on top of a polyglot ecosystem of Java and Go services built on Kafka. Some older apps still run on JavaScript, Redux and webpack, and you’ll work in those too
• We run experiments in GrowthBook, define our tracking events in Avo, and handle billing with Chargebee
• We love high velocity, and AI is at the heart of how we build. We expect our engineers to use LLM and agentic tools (specs, agent loops, and agentic workflows) to iterate fast and build systems. We stay provider agnostic (Anthropic, OpenAI, Cursor, local models, or self hosted models in the cloud)
• We pair that speed with deep pride in ownership. A natural READ THE CODE mindset, where you keep a full understanding of, and full accountability for, every line you ship
• Drive Growth: Design, build, and run experiments across the user journey (acquisition, activation, conversion, retention) and turn the results into product decisions
• Own the Feature: Take ideas from hypothesis to production, end to end, wherever the work lives in the stack
• Ship with AI: Use LLM and agentic tools as your default way of working to move fast, while keeping total ownership and full understanding of the generated code
• Build the Frontend: Create fast, accessible, and scalable web applications with React.js, Next.js, and TypeScript
• Go Beyond the Frontend: Extend backend services and GraphQL APIs when an experiment needs it, with Apollo Client managing data on the client
• Measure What Matters: Instrument features with clean tracking that respects each user’s consent choices, so every test produces data the team can trust
• Optimize for Speed: Tune performance for speed, scale, and smooth experiences across devices and platforms
• Translate the Hard Stuff: Work closely with product managers, UX designers, data analysts, and fellow engineers to turn complex scheduling requirements into clean, elegant solutions

You are a proactive builder and a continuous learner. You thrive on shipping products that matter. You always find a way to reach the goalWhether your background is frontend or fullstack, we care most about mindset. With AI in your toolkit, you are ready to work on anything: you’ll follow a problem wherever it lives in the stack and solve it in the right placeIf you get excited by A/B tests, funnels, and the exact precision needed when you build products around Time itself, you’ll find a stimulating environment hereYou’ll thrive here if you are a builder who values customer impact as much as clean code, and who is happy to work on anything to reach the goalThe AI Mindset: You are AI savvy. LLM and agentic tools are part of how you work every day, and you use them to deliver across the whole stackThe Toolkit: Professional experience with JavaScript, TypeScript, React.js, and Next.js, and comfort working in older JavaScript and Redux codeThe Fullstack Mindset: Frontend or fullstack, you are curious beyond your primary area, and you can read, debug, and change code across the stackThe Data Layer: Experience building production ready applications with client side data fetching via GraphQL (Apollo)The Growth Experience: Proven, hands on experience with growth topics and product experimentation, such as A/B testing, funnel optimization, and activation or conversion workThe Foundation: A Bachelor’s in Computer Science, a related technical field, or equal practical experienceThe Backend Edge: Professional experience building backend services, ideally in Java, and designing GraphQL APIsThe Distributed Layer: Practical experience with microservices and event driven architectures built on Kafka. Go is a plusThe Data Craft: Comfort with experimentation platforms and feature flags such as GrowthBook, tracking plans such as Avo, product analytics, and the statistics behind a sound testThe Billing Side: Experience with subscription billing and payments, ideally ChargebeeThe Architecture: A strong architectural mind for component isolation, server side rendering (SSR), and static site generation (SSG) strategiesThe Craft: Experience with frontend performance optimization, responsive design, and modern browser APIs

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