Principal Software Engineer – Cyber Security Research – On Site Barcelona

Opportunity We are a next generation Cyber Security Research start‑up based in Barcelona that needs a Principal Software Engineer. You don’t need Cyber Security experience to apply. This is a zero‑to‑one role: architect, coder, system designer, and future team builder rolled into one. You will be required to work on site 5 days a week in Barcelona.

What You’ll Do

Partner with founders to translate a bold product vision into a world‑class technical architecture and initial codebase.

Design and build complex, high‑throughput distributed systems optimized for hybrid, air‑gapped, and on‑prem deployments.

Own the core workflow automation/orchestration engine, including deep understanding of its inner workings, customization, and extensibility.

Build AI‑ready data pipelines and architecture so we can integrate advanced capabilities without rewriting core systems later.

Establish production‑grade Kubernetes infrastructure tailored for highly confidential environments.

Scout, vet, and direct high‑quality contractors/vendors to accelerate delivery while embedding exceptional engineering standards.

Lay the cultural and technical bedrock for a permanent world‑class engineering team.

Technical Expectations

Strong backend experience with Python, Go, or Rust.





Solid experience with distributed systems and workflow automation engines.

Front‑end understanding is a plus.

Previous experience building complex systems from scratch.

What We’re Looking For

Proven experience designing and shipping complex, secure, enterprise‑grade or mission‑critical software (Gov Tech, Defence Tech, or critical infrastructure experience is a strong advantage).

Deep expertise in distributed systems, self‑hosted/hybrid architectures, Kubernetes in restricted environments, and workflow automation platforms (Temporal, Airflow, custom engines etc).

A builder’s mindset who loves writing code and multiplying impact through smart use of external talent.

Ability to move fluidly between high‑level product strategy and low‑level technical decisions.

Nice to Haves

Prior startup experience.

AI/agentic workflows.

Big data architecture understanding.

What We Offer

Top‑tier compensation and meaningful performance bonuses tied to real impact.

Direct collaboration with founders and genuine product ownership.

The agility and autonomy of a startup backed by the stability of a profitable, debt‑free company.

The chance to build technology that directly helps defend against sophisticated cyber threats.

Principal Software Engineer • Barcelona, Kingdom Of Spain, ES

📌 Principal Software Engineer (Madrid)
🏢 CBSbutler
📍 Madrid