Senior Product Engineer

Job title: Senior Product Engineer (AI-Native)

Location: Remote (Within Spain)

Contract: Freelance/Contract

We're searching for a Product Engineer to support in building a multiplatform AI-powered document system, serving hundreds of thousands of users every month.

Key Responsibilities

• Build and maintain the core multiplatform document system, owning features end-to-end from idea to production across React frontends, Node.js/Express backends, and PostgreSQL/Databricks data layers
• Design and orchestrate agentic AI workflows using LangGraph, Claude Agent SDK, and MCP protocols; integrate LLMs into product features via prompt chains, tool calling, and function execution
• Proactively instrument features, measure impact, seek user feedback, and iterate based on what you discover treating metrics as a compass, not a report card
• B...