AI Solution Engineer - Full-stack / Rails Engineer (Barcelona)

Recent experience playing with LLMs is now mandatory, and you have already adopted AI in your day-to-day tasks. Building with LLMs and managing non-deterministic output is not scary to you.

If you are relentless, deeply caring about delivering value & ownership, and looking to join an early, hard-working team, we want you . We are seeking someone who is looking to embrace a new challenge and commit to it 100%.

Your diploma doesn't matter to us; we only care about your skills, your sense of ownership, and drive.

Yuma is building a next-generation orchestration platform that deploys autonomous AI agents dedicated to customer support in e-commerce. We already support 150+ paying merchants and help them automate up to 80% of their customer tickets freeing human agents for higher-value conversations. Founded by Guillaume Luccisano (3rd-time YC founder) at the end of 2022, Yuma is one of the leaders in the AI Support Automation space with 10+ consecutive months of double-digit growth. We are now a team of 30 passionate and ambitious people based between Paris, Barcelona and Boston and have grown revenue 5x in 2025. We aim to repeat this trajectory in 2026. The scale-up phase is fully underway. We remain a small team of 5 engineers, but we are intense and we move very quickly! Fast iteration is key. In the past 2 years since Yuma's founding, we've built a lot, but there is still much more to do! We operate at startup speed and handle everything: product iterations, A/B testing, LLM research, AI Agents pipeline, new feature development, performance optimizations, and more. We are intensely focused on delivering value to our users and on product excellence. That is the only thing that matters. Our backend is a standard Ruby on Rails API powered by PostgreSQL, Redis, and Sidekiq. Our frontend uses Next.js and React. We already handle a significant load, ingesting and processing millions of support tickets per month and millions of e-commerce data points per day. We are definitely not a 9-to-5 team, and we are heavily committed to delivering excellence throughout our craft. You have led and built multiple large Rails applications, and you always strive for excellence. You are pragmatic, making the right trade-offs that favor speed of iteration while maintaining high product quality. You are driven by delivering the best experience and value to your users. You might have a preference for working on backend projects, but you aren't afraid of frontend work. Rails has no secrets for you.