Senior Backend Engineer - Semantic AI for Enterprise Data

Cirql One; Barcelona; Hybrid; EUR 90,000 - 130,000; Full time

Job summary

Cirql One is building an enterprise semantic intelligence layer that makes data meaning explicit and actionable for AI systems. As a backend engineer, you will own the semantic catalog, design scalable data structures, and ship features end-to-end—from data extraction to governance—while collaborating with cross-functional teams.

You’ll work on a small, focused team in a hybrid setup in Barcelona, shaping the product and guiding technical decisions that affect customers.

Qualifications

• 4+ years of professional backend development in Python, building data-intensive or distributed systems.
• Production experience with FastAPI or a comparable Python web framework (FastAPI preferred), and a track record of designing clean, well-documented APIs.
• Solid command of PostgreSQL and ORM-based data modeling.
• Proven ability to translate customer and business requirements into well-architected technical solutions.
• Hands-on experience deploying and running containerized services in production on Azure, GCP or similar, including CI/CD, managing environments (dev/staging/prod), and infrastructure as code (e.g. Terraform).
• Demonstrated use of AI coding tools (e.g. Claude Code, Cursor) in production workflows, with strong judgment around validation and quality control.
• You write automated tests as part of the work, not after it, and design test scenarios that catch real-world edge cases.
• Fluent English, written and spoken.
• Background in semantic systems: knowledge graphs, ontologies, metadata catalogs, or data governance tooling.
• Experience building AI agents or agentic workflows, including Model Context Protocol (MCP) integrations and guardrails for AI systems.

Responsibilities

• Build the semantic core. Design and evolve the platform that transforms raw enterprise data into structured, business-accurate meaning usable by AI agents, from data extraction pipelines to semantic storage, versioning, and governance.
• Own features end-to-end. Take a problem from schema design through backend logic and APIs to how it surfaces in the product. You won’t hand things off. You’ll see them through and care about every layer.
• Shape architecture. Make principled technical decisions and explain them clearly. Balance long-term platform coherence with the speed that early-stage demands. Push back when it matters and adapt when it doesn't.
• Amplify your impact with AI. Use the best AI tools across design, implementation, testing, and documentation to move faster, without compromising on correctness and reliability.

Skills

Backend development (Python)

API design

Testing

Tools

FastAPI

PostgreSQL

Terraform

CI/CD

Azure/GCP

Claude Code

Cursor

Job description

Cirql One is building an enterprise semantic intelligence layer that makes data meaning explicit and actionable for AI systems. As a backend engineer, you will own the semantic catalog, design scalable data structures, and ship features end-to-end—from data extraction to governance—while collaborating with cross-functional teams.

You’ll work on a small, focused team in a hybrid setup in Barcelona, shaping the product and guiding technical decisions that affect customers.