Ciklum is looking for a Senior Full Stack Developer to join our team full-time in Ukraine. We are a custom product engineering company that supports both multinational organizations and scaling startups to solve their most complex business challenges. With a global team of over 4,000 highly skilled developers, consultants, analysts and product owners, we engineer technology that redefines industries and shapes the way people live. About the role: The Client is a 3-month-old, seed-funded ad-tech startup building infrastructure analytics for publishers. Having successfully launched a POC with design partners, they are now transitioning from a solo-founder codebase to a founding engineering team of four. The focus is on high-seniority, autonomous developers who can thrive in a fast-paced, "startup-mode" environment without heavy management. Responsibilities: - Design, develop, and maintain scalable full-stack applications using React, Node.js - Develop the core product offering implemented to track and analyse billions of events on websites and apps - Develop integrations with Supply-Side Platforms (SSPs) and Demand-Side Platforms (DSPs) - Integrate AI/ML capabilities into our platform, including LLM APIs and on-premise model deployments - Build agentic workflows and AI-powered automation to enhance platform capabilities - Collaborate with product, data science, and engineering teams to deliver end-to-end solutions - Mentor junior developers and contribute to engineering best practices Requirements: - 5+ years of professional software development experience - Strong proficiency in JavaScript/TypeScript, React, and Node.js - Experience building high-performance, low-latency distributed systems - Strong understanding of RESTful APIs, microservices architecture, and cloud platforms (AWS/GCP) - Experience with databases (SQL and NoSQL) and data streaming technologies - Excellent problem-solving skills and ability to work autonomously - Strong communication skills and collaborative mindset What`s in it for you? - Strong community: Work alongside top professionals in a friendly, open-door environment - Growth focus: Take on large-scale projects with a global impact and expand your expertise - Tailored learning: Boost your skills with internal events (meetups, conferences, workshops), Udemy access, language courses, and company-paid certifications - Endless opportunities: Explore diverse domains through internal mobility, finding the best fit to gain hands-on experience with cutting-edge technologies - Flexibility: Enjoy radical flexibility – work remotely or from an office, your choice - Care: We’ve got you covered with company-paid medical insurance, mental health support, and financial & legal consultations About us: At Ciklum, we are always exploring innovations, empowering each other to achieve more, and engineering solutions that matter. With us, you’ll work with cutting-edge technologies, contribute to impactful projects, and be part of a One Team culture that values collaboration and progress. As one of Ukraine’s largest IT companies and a top employer recognized by Forbes, we’ve spent over 20 years delivering meaningful tech solutions. We proudly support diverse talent and military veterans, recognizing their unique skills and perspectives they bring to shaping the future. Want to learn more about us? Follow us on Instagram, Facebook, LinkedIn. Explore, empower, engineer with Ciklum! Interested already? We would love to get to know you! Submit your application. We can’t wait to see you at Ciklum.