Senior Full-Stack Software Engineer, Applied AI 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 Software Engineer, Applied AI based in Spain.

This is a high-impact engineering role at the intersection of full-stack product development and applied artificial intelligence, where you will help shape and ship AI-powered features used at scale. You will work across a modern web stack to build end-to-end AI experiences, from backend services and data pipelines to frontend interfaces that surface intelligent functionality. The role focuses heavily on experimentation, iteration, and real-world impact, particularly through the use of large language models and production AI systems. You will contribute to building AI agents, retrieval-augmented generation systems, evaluation frameworks, and infrastructure for reliable LLM inference. Working closely with product, design, and engineering leadership, you will help translate ideas into tested, measurable product improvements. The environment is fast-moving, highly autonomous, and built around strong ownership and continuous learning.

You will design, build, and optimize full-stack AI features end-to-end while contributing to experimentation, system reliability, and continuous product improvement across AI-powered experiences.

• Ship full-stack AI features using Ruby on Rails and React across production systems
• Design and run experiments, including A/B tests and AI evaluations, to measure feature impact
• Build and maintain AI infrastructure components, including LLM-based systems and inference workflows
• Develop and improve RAG systems, AI agents, and other applied LLM-based solutions
• Optimize performance, scalability, and reliability of AI-driven features in production
• Collaborate closely with product managers, designers, and engineering peers to define feature direction
• Continuously improve engineering processes and tooling to support rapid AI iteration
• Stay current with emerging AI research and translate insights into practical implementations
• Ensure high standards of code quality, system design, and user experience across releases

You bring strong full-stack engineering experience at scale, combined with hands-on exposure to building and shipping AI-powered features in real production environments. You are comfortable working across ambiguity, experimentation, and fast iteration cycles.

• 6+ years of experience as a full-stack engineer on high-traffic production applications
• Strong proficiency in Ruby on Rails, ReactJS, and relational databases (PostgreSQL/MySQL)
• Hands-on experience building production AI features such as RAG systems, AI agents, or LLM-powered tools
• Proven ability to design and run experiments (A/B testing, evaluation frameworks, iterative product testing)
• Strong understanding of backend and frontend systems, with ability to work across the stack
• Experience working in scalable, performance-sensitive environments
• Comfort operating in fast-paced, ambiguous environments with evolving requirements
• Strong collaboration skills and ability to work closely with cross-functional teams
• Excellent English communication skills (written and verbal)
• Strong bias toward action, experimentation, and measurable outcomes

• Fully remote work from anywhere
• Competitive compensation with regular performance reviews and equity opportunities
• 35 days of paid time off annually
• Paid sabbatical after 5 years of service
• Comprehensive medical coverage for employees and eligible family members
• Home office setup stipend
• Learning and development budget for professional growth
• Annual company retreats in international locations
• Parental leave and family support benefits
• Strong autonomy with a high-trust, outcomes-focused culture
• Inclusive, global team environment with diverse backgrounds and perspectives