Principal Data Engineer in London

About Harmonic Security

Harmonic Security lets teams adopt AI tools safely by protecting sensitive data in real time with minimal effort. It gives enterprises full control and stops leaks so that their teams can innovate confidently. We are led by cybersecurity experts and backed by top investors including N47, Ten Eleven Ventures, and In-Q-Tel. We have achieved early traction and strong product-market fit with a world-class team, and we are now focused on scaling the data foundations that power our product, analytics, and machine learning. This is an opportunity to join early, take real ownership of core data systems, and help define how data is modeled, moved, and trusted in a new category of AI security.

About the Team

Our Product Delivery team is the engine that turns vision into impact. We ship early and often, getting valuable features into the hands of customers quickly and iterating from there. We work in the open by default, sharing progress and ideas, and we trust each other to own outcomes. We are a small but mighty crew where every person plays a critical role and we are committed to using AI to work smarter and faster.

About the Role

We are looking for a Senior Data Engineer to design and build robust, open, and scalable data systems that power everything from product analytics to machine learning to internal tooling. You will play a pivotal role in shaping how data moves through our systems using open-source tools and open standards whenever possible. This is a hands-on role for someone who relishes in the details of data design, loves building systems that are observable and reproducible, and believes deeply in avoiding vendor lock-in. This role combines backend engineering discipline with a product mindset.

What You Will Do

• Own data pipelines and deliveries end to end, from design through production and iteration.
• Design, build, and evolve scalable data architectures for data-intensive workloads supporting analytics, reporting, and downstream consumers.
• Implement reliable ingestion, transformation, and enrichment pipelines for event-based data.
• Develop and maintain well-modeled, reproducible data assets that are easy to discover and reuse across teams.
• Partner closely with engineering, machine learning, and product teams to ensure data is accurate, timely and fit for purpose.
• Build strong observability into data workflows, enabling monitoring, debugging, and performance tuning.
• Ship fast, learn fast; continuously delivering value and refining based on user feedback.

What Success Looks Like

• Data products and pipelines you have built are widely adopted and trusted by engineering, product and machine learning teams.
• You can quickly translate product and business requirements into clear, well-structured data models and datasets.
• Reliability, performance, scalability, and data quality are built into every data workflow and release.
• You are seen as a trusted partner by product, design and engineering peers.

What You Bring

• Strong experience building and operating data-intensive systems using Java or Python and SQL.
• Solid expertise in data modeling, schema design, and managing analytical data at scale in cloud environments.
• Experience with event-driven data architectures and streaming-based ingestion patterns.
• A preference for open standards, interoperability, and maintainable, vendor-neutral system design.
• Excellent collaboration and communication skills in cross-functional teams.

You Might Be a Fit if You...

• Love solving complex data challenges with simplicity and speed.
• Thrive in fast-paced startup environments where ambiguity is the norm.
• Enjoy shaping culture and engineering practices, not just writing code.
• See AI as a tool to help you build smarter, faster, and better.

Why Join Us

This isn’t just a job; it’s an opportunity to be part of a team that is redefining cybersecurity. We believe today’s talent is tomorrow’s success, and we are committed to creating an environment where you can do the best work of your life.

• Competitive pay and meaningful equity with a direct stake in Harmonic’s success.
• Comprehensive benefits, pension plan, generous PTO, and flexible hybrid work.
• A small, passionate team that values transparency, creativity, and learning.
• Thoughtful leadership that cares deeply about growth, impact, and people.
• Annual global offsites (past trips include Lisbon and Nashville).
• The chance to directly shape both our product and our culture as we build a category-defining company.

Harmonic’s Core Values

• Flourish in the Unknown: We relish being thrown into new, unfamiliar situations that require initiative and rapid decision-making. We orient ourselves quickly and deliver results with minimal guidance.
• Never Full: We never hesitate to raise our hands and take on challenges to assist those in need. We hunger for opportunities to learn and do more.
• Perfect Harmony: We have a genuine willingness to assist and support one another to create cohesion and unity. We foster success through collaboration and honest sharing of feedback and ideas, enabling everyone to grow and produce their best work.