Senior Fullstack Engineer (m/f/d)

Fullstack Engineer (m/f/d) Berlin, Bangalore, Remote Hello 👋 I am Servesh , Co- founder and CTO at Kayzen, and I am now looking for a Fullstack Engineer to join our Console team. 🙌 But wait, you have not heard of Kayzen before? 😃 Kayzen is a mobile demand-side platform (DSP) dedicated to democratizing programmatic advertising. We enable leading apps, agencies, media buyers, and brands to run programmatic customer acquisition, retargeting, and brand performance campaigns through its self-serve and managed service options. Built on the three core pillars of performance, transparency, and control, Kayzen powers the world’s best mobile marketing teams with bespoke solutions that fuel business growth and deliver a competitive advantage. With an unprecedented scale of 160B+ daily ad requests from 1.6B+ unique users worldwide, we serve up to 1B+ ads per day in 180 countries. Kayzen is accessible through our APIs and user interface. The Team The Console team owns the user-facing applications and interfaces that power the Kayzen platform — from our self-serve campaign management dashboard and real-time reporting suite to internal tooling used by our managed service teams. We work closely with product managers, designers, backend engineers, and data teams to deliver seamless, high-performance experiences. We are responsible for some of the most impactful work at Kayzen, including: “The Console” which is the face of Kayzen we are very proud of. Complex features which surface a lot of backend infrastructure via console Almost 100% uptime with very well planned & executed project management Sounds interesting. Isn’t it? About the Role We are looking for a coding-first Fullstack Engineer who thrives on turning complex product requirements into high-performance UIs. You should be comfortable working across the stack, contributing to architecture discussions, and be an early adopter of AI-assisted engineering (e.g., Claude Code, Cursor, Copilot) in your daily coding workflow. This role is a strong individual contributor position with room to grow into deeper technical ownership over time. Responsibilities Core responsibilities Design, build, and maintain high-quality features across the Fullstack stack, from UI to API integration Write clean, well-tested, production-ready code and actively participate in code reviews Collaborate closely with Product, Design, QA, and Backend teams to deliver cohesive, user-centric features Contribute to technical decisions around architecture, tooling, and best practices within the team Take ownership of features end to end, from planning through deployment and monitoring Hands-on AI Implementation Integrate AI-powered coding agents and automated LLM-based testing into your daily development cycle Contribute to building 'AI-First' UI patterns, working alongside the LLM Platform team on generative, prompt-driven interfaces Stay current with emerging AI-assisted development tools and bring relevant ones back to the team Project & Execution Management Break down assigned product requirements into clear, actionable engineering tasks Deliver work reliably within sprint commitments, flagging blockers or scope changes early Balance new feature delivery with addressing technical debt in the codebase you work on Requirements Fullstack Technical Excellence (Core Focus) 5+ years of professional Fullstack development experience with modern JavaScript/TypeScript Solid expertise in at least one major framework (React, Angular, or Vue) and its ecosystem Strong understanding of HTML5, CSS3, responsive design, and cross-browser compatibility Experience building data-heavy UIs, ideally including real-time data visualization Good grasp of Fullstack performance optimization, including bundle size, rendering, lazy loading, and caching strategies Experience with state management patterns (Redux, MobX, Zustand, or similar) Working knowledge of Fullstack testing methodologies, unit, integration, and end-to-end (Jest, Cypress, Playwright, or similar) Comfortable working with design systems and shared component libraries Experience using AI-assisted development tools (e.g., Claude Code) to boost engineering productivity Engineering Maturity Experience contributing to Fullstack architecture decisions on production applications Solid understanding of APIs, RESTful services, GraphQL, and system design fundamentals Ability to give and receive constructive feedback through code reviews Good communication skills, able to explain technical decisions clearly to teammates and stakeholders Startup Mindset Bias for shipping and iteration, you deliver incrementally and learn from real users Comfortable with ambiguity and rapid change in a fast-paced environment Thinking in terms of leverage and reuse, not one-off solutions Pragmatic about trade-offs between perfectionism and speed of delivery Less About Developers who prefer working in isolation on narrowly scoped tickets without engaging with the wider product context. We need someone who wants to understand the "why" behind the work and contribute ideas, not just execute tasks. Nice to Have Familiarity with ad-tech, real-time bidding platforms, or high-traffic data products Contributions to open-source Fullstack projects or community involvement Experience building Fullstack interfaces for AI/ML-powered products (e.g., chatbots, recommendation engines, AI-generated content displays) Familiarity with LLM APIs and prompt-driven UI patterns What do we offer? Exceptional career growth and learning opportunity A unique opportunity to be part of an experienced team of industry experts and entrepreneurs who bring massive change to the Adtech market A fun, driven, and multinational team located across Germany, India, UK, Argentina, Ukraine, Turkey, Spain and many more countries A flexible work-from-home arrangement A 500-dollar home-office setup budget A 1000-dollar annual learning and development budget