Senior Backend Engineer

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

At Cirql One, we are building the foundational layer that connects enterprise data to AI: a layer that doesn't just relay information, but genuinely understands it, making business meaning explicit, trusted, and actionable at scale.

The problem we're solving is deceptively hard. SAP runs the core operations of more than 90% of Fortune 500 companies. The data is reliable. The meaning, however, is buried inside 30 years of configurations, customizations, and undocumented logic that no AI system can interpret on its own. We've spent decades inside these environments. We know the problem intimately, and we've built our company around a single conviction: before AI can truly scale inside the enterprise, business meaning must be made explicit.

Cirql One is that missing link: an enterprise semantic intelligence layer that gives AI models and agents a shared, business-accurate understanding of enterprise data. Our vision is to become the system of reason sitting above SAP, where intelligence, metrics, and AI automation are defined, governed, and executed.

This is a hands-on role at the heart of the product. Reporting directly to our Head of R&D, you’ll work on the semantic catalog, the core of Cirql One, where enterprise data structures become governed, versioned business meaning. You’ll be close to the customer: partnering with solutions engineers, product, and customer success to gather requirements, challenge assumptions, and shape what we build next. As a small team, we set priorities together, and your scope will evolve with the product.

Tasks

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.

How You Work

Pragmatic by design. You weigh trade-offs clearly and reach for the right pattern, library, or approach for the problem at hand, not out of habit. You can defend that choice clearly.

Sharp thinking. You break down complex problems methodically and reach well-reasoned conclusions. You know how to separate signal from noise, and you're comfortable making decisions under uncertainty without waiting for the perfect answer.

Clear communicator. You express ideas precisely, in code, in writing, and in conversation. You can walk a non-technical colleague through a technical decision without oversimplifying it.

Collaborative by default. You share knowledge freely, back the best idea regardless of where it came from, and make the people around you better. You're someone colleagues genuinely want to build with.

Ownership mindset. You take initiative on real problems early, don’t wait for permission, and are trusted to own the outcome.

Cross-functional. You want to understand the business problem behind the ticket. You’re eager to learn how enterprises actually run on data, and you seek out the people closest to customers to get it right.

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.

Nice to have

Experience designing and maintaining data pipelines and ETL/ELT workflows, ideally with a cloud data warehouse such as Snowflake.

Exposure to SAP data structures or other enterprise ERP environments. If you don’t have it, we’ll teach you.

Experience with microservices or event-driven architectures.

Full transparency. No filtered updates. Everyone knows what we’re building, how the business is doing, and where we’re going.

Regular team onsites. We get together in person to plan, build, and spend time as a team.

Competitive compensation. Pay that reflects the seniority and impact of the role.

Hybrid and flexible. A hybrid setup at our Barcelona office, with the flexibility to organize your week around your work and your life.

Room to grow. We’re scaling deliberately, and your scope grows with the company.

People who care. Everyone is deeply invested in the problem and committed to doing the work well.