Principal Software Engineer

Principal Software Engineer – Cyber Security Research - On Site Barcelona - Zero to One Build

I'm looking for a Principal Software Engineer to join a next generation Cyber Security Research start up based in Barcelona (You do not need Cyber Security experience to apply), who are building mission critical systems that protect national security interests across Europe. Given the importance of this position, we need someone who can be on site 5 days a week in Barcelona.

You’ll be solving hard problems around distributed execution, workflow durability, secure orchestration, disconnected environments, and large scale system resilience, sitting at the intersection of cybersecurity and government technology. It’s designed for self hosted and hybrid environments where data sovereignty, privacy, and uncompromising security are non negotiables. They're not building another SaaS tool, they're building resilient, sophisticated infrastructure that matters.

The Opportunity:

They're looking for a Principal Software Engineer to be the first engineering hire on this project and technical founder of this new division. You won’t be implementing someone else’s spec, you’ll co design the product and architecture directly with the founders, write production code from day one, and lay the foundation for everything that follows.

This is a true zero-to-one role: architect, coder, system designer, and future team builder rolled into one.

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 optimised for hybrid, air gapped, and on prem deployments.
• Own the core workflow automation/orchestration engine, including deep understanding of its inner workings, customisation, 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 with Python, Go, or Rust.
• Solid distributed systems and workflow automation engine experience a big plus
• Frontend understanding is a plus.
• You’ve built complex systems from scratch before.

What We’re Looking For:

• Proven experience designing and shipping complex, secure, enterprise grade or mission critical software (GovTech, DefenceTech, 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 start up experience, AI/agentic workflows, big data architecture understanding

What We Offer:

• Top tier compensation + meaningful performance bonuses tied to real impact.
• Direct collaboration with founders and genuine product ownership.
• The agility and autonomy of a start up backed by the stability of a profitable, debt free company.
• The chance to build technology that directly helps defend against sophisticated cyber threats.

If you’re a high calibre Principal/Staff/Architect level engineer who gets excited by building complex systems from nothing, shaping product direction, and creating the foundation for an entire new division, we want to hear from you.

This is a rare opportunity to own something significant at the earliest stage.

Please send through an updated CV and I will give you a call straight away.

Looking forward to connecting with exceptional builders!