AI Product Focus - Senior Full Stack / Rails Engineer (Boston)

About Yuma AI

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 25 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.

About The Role

This is a foundational role. You will be joining Yuma as one of the core engineers on a tight, high-performing team of 5. We move fast, iterate aggressively, and care deeply about product quality and user value. Over the past two years, we’ve built an impressive amount of product surface area, AI systems, and automation. Yet what lies ahead is even bigger. As we scale our platform, models, and AI agents, your work will have a direct and immediate impact on the experience of thousands of users.

This role goes far beyond classical backend development. You will work across the full product lifecycle: new features, A/B tests, model integrations, AI agent pipelines, and performance optimization. If you enjoy working at the intersection of backend engineering, product iteration, and applied AI, you will thrive here.

Backend Engineering Architect

• Build and scale large Ruby on Rails applications
• Own major systems within our Rails API, including performance, reliability, and maintainability
• Manage PostgreSQL at scale: schema design, indexing, performance diagnostics
• Maintain and optimize Redis + Sidekiq pipelines for high-throughput workloads
• Lead backend-heavy feature projects, from design to deployment

AI / LLM Systems

• Integrate, evaluate, and iterate on LLM providers and models
• Design systems that manage non-deterministic model outputs safely and predictably
• Build and own A/B tests, eval pipelines, and agentic workflows
• Optimize for latency, reliability, and cost across LLM-heavy features
• Contribute directly to prompts, agents, and AI system architecture

Product & Full-Stack Contribution

• Collaborate tightly with founders and engineers to define product requirements
• Jump into frontend (Next.js/React) when needed to ship features end-to-end
• Run rapid product iterations: fast feedback loops, experimentation, data-driven decisions
• Maintain a high bar for product quality while optimizing for speed of execution

The Ideal You

• Have 5–10+ years of experience building and scaling production Rails applications
• Rails has no secrets for you : you know how to ship quickly and safely
• Are pragmatic: you make thoughtful trade-offs that maximize user value and iteration speed
• Naturally take ownership and thrive in high-velocity environments
• Have recent, hands-on experience with LLMs and already use AI in your day-to-day workflow
• Are comfortable navigating ambiguity, experimenting, and working with non-deterministic systems
• Can contribute across the stack when needed (backend-first, but not backend-only)
• Deeply care about product quality, speed, and delivering a great user experience

The Alternative You

• If you're still early in your career but see yourself becoming the engineer described above within the next 2–3 years, don’t hesitate. We consistently leave room for raw talent and high potential, especially for people who learn fast, care deeply, and want to grow.