The Opportunity: Join our product engineering team in the US to build features that directly impact how customers experience and adopt our platform. This role bridges technical execution and product thinking - you'll ship user-facing features while making architectural decisions across the entire stack. You'll work end-to-end: designing interfaces, building APIs, optimizing performance, and deploying to production. We move fast, iterate with users, and expect engineers to own problems from concept to launch. We sponsor visas for qualified candidates.

Responsibilities

Build full-stack features from UI components to backend services

Design and implement responsive, intuitive user interfaces with React

Develop high-performance APIs using FastAPI and async Python

Work with LLM integrations, prompt engineering, and AI-powered workflows

Deploy and monitor features across our AWS infrastructure

Gather user feedback and iterate rapidly on what you ship

Technical Requirements





Strong full-stack development experience (frontend + backend)

Proficient in React and modern JavaScript/TypeScript

Python skills with FastAPI or similar frameworks

Experience with PostgreSQL, Redis, and async patterns

Comfortable with AWS/Azure/GCP, deployment pipelines, and infrastructure basics

Product mindset - you care about user experience and customers, not just code

Nice to Have

Experience building with LLMs and AI-powered features

Browser automation or headless browser technologies

Design sensibility and attention to UI/UX details

Previous startup or 0-to-1 product experience

Why Karumi

Meaningful equity stake in a backed, fast-growing company

End-to-end ownership of features users interact with daily

Direct impact on product direction and company trajectory

Small team where shipping matters more than process

Visa sponsorship available

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📌 Product Engineer (Full-Stack) (Madrid)
🏢 Karumi (YC F25)
📍 Madrid