Senior Full stack Engineer (New Business) in Spain at Jobgether

This position is listed on behalf of a partner company, who manages all applications and next steps. Our partner is looking for a Senior Full Stack Engineer (New Business) based in Spain.

This role sits at the core of a next-generation data annotation platform powering the infrastructure behind modern AI systems. You will be building tools that enable large-scale dataset processing across images, audio, video, and documents, transforming raw data into structured, high-quality inputs for machine learning workflows. The environment is highly technical and fast-moving, focused on solving complex UI, scalability, and architecture challenges across a modern JavaScript stack. You will work closely with product and engineering peers to design systems that are both performant and intuitive, ensuring the platform can handle massive volumes of multimodal data. This is a hands-on role with strong ownership, where you will influence technical direction and contribute directly to product evolution. It’s an opportunity to work at the intersection of full stack engineering and AI infrastructure in a highly innovative setting.

• Design, build, and maintain scalable full stack features using Node.js, React (Next.js), and TypeScript for a high-traffic data annotation platform.
• Take ownership of features from concept to production, including architectural design, implementation, testing, and deployment.
• Develop and optimize systems that handle large-scale multimodal datasets such as images, audio, video, and documents.
• Collaborate with engineers and product teams to define technical requirements and propose scalable architectural solutions.
• Review code, mentor teammates, and contribute to engineering best practices and a culture of continuous improvement.
• Experiment with AI-driven tools and workflows to enhance productivity and platform capabilities.
• Ensure system performance, reliability, and maintainability across complex user workflows and data-heavy operations.

The ideal candidate is a strong full stack engineer with deep experience in modern JavaScript ecosystems and a strong architectural mindset. You are comfortable working across frontend and backend systems, making trade-offs between speed, scalability, and long-term maintainability.

• Expert-level experience with TypeScript, JavaScript, Node.js, and React (Next.js).
• Strong understanding of backend fundamentals, including PostgreSQL or Supabase, clean code principles, and testing practices.
• Proven ability to design scalable system architectures and evaluate technical trade-offs effectively.
• Strong problem-solving mindset with the ability to compare multiple solutions and choose optimal implementations.
• Experience working in fast-paced environments with evolving product requirements.
• Solid communication skills and ability to collaborate across engineering and product teams.
• Nice to have: experience with Tailwind CSS and design systems for consistent UI development.
• Nice to have: familiarity with Python for AI/ML or LLM-related integrations.
• Nice to have: experience with CI/CD pipelines and deployment tools such as Vercel.
• Nice to have: exposure to data labeling systems, media processing, or document-heavy workflows.

• Competitive compensation package aligned with experience
• Fully remote-friendly working model
• Opportunity to build infrastructure powering next-generation AI systems
• High ownership role with direct impact on product architecture and direction
• Exposure to large-scale, multimodal data processing systems
• Collaborative, highly skilled engineering environment
• Strong focus on innovation, experimentation, and technical growth
• Career progression opportunities into senior technical or leadership paths