At Quadrivia, we have brought together some of the smartest and most passionate people in the sector to work on an ambitious goal: help make healthcare accessible and affordable for everyone on earth, by solving the chronic imbalance between the growing demand for medical care and the constrained supply of clinical skills. While externally we are starting with creating the world's most comprehensive and customizable clinical assistant to deliver routine tasks for clinicians, internally we are pioneering a new way to run a company.
The Role
You'll build and run Cortex, the core AI architecture behind Qu, and the services that sit on top of it: automated AI audits, patient simulators, retrieval (RAG), and the escalation agents that take over in red-guardrail situations. This is a backend role first. The job is to make our AI systems reliable, fast, and observable in production, not to invent new ML. You own the software underneath the agents.
We're a small team that ships real systems. We've built our entire AI-driven evaluation system, our voice orchestrator,



and a multi-hierarchical RAG platform from scratch.

What You'll Do
- Design and maintain robust, modular backend systems using clean architectural (SOLID) principles to ensure long-term maintainability, scalability and flexibility as the agentic stack evolves.
- Own Cortex end-to-end: architecture, API design, service boundaries, reliability targets, and proactively managing failure modes.
- Build the platform services around it. The automated audit and eval pipeline, patient simulators for testing agents at scale, and the retrieval layer.
- Write fast, well-tested Python services with FastAPI, asyncio, and pydantic, and get the queues, caching, and data stores right.
- Wire up the multi-agent orchestration: routing between agents, shared state, and clean tool interfaces.
- Engineer the RAG pipeline for high-signal retrieval (chunking, hybrid search, re-ranking, caching) and prove the grounding holds.
- Make th

📌 AI Engineer Backend (Barcelona)
🏢 Quadrivia
📍 Barcelona