Senior Backend Engineer -UK

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 product-market fit with a world-class team, and we are now focused on building a category-defining company. This is your opportunity to join us early and shape not just a product, but a category.

How We Work: AI-First by Design

Harmonic exists to help enterprises adopt AI safely and at scale. We hold ourselves to that same standard. Everyone here actively leverages AI tools to perform their best work — from deep research and writing to building robust processes and automating complex workflows. We expect every new hire to bring a genuine curiosity for AI and a commitment to using it to work smarter, faster, and with greater creativity.

For some, this involves tinkering and remaining open to emerging tools; for others, it means architecting entirely new systems with AI at the core. We will be transparent about expectations for every role and provide the tools and support needed for you to thrive.

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’re a small but mighty crew where every person plays a critical role and we’re committed to using AI to work smarter and faster.

About the Role

We’re looking for a Backend Engineer who has an appreciation for all things security and system interconnectivity. This is a very hands-on technical role where you will be responsible for designing, building and maintaining scalable integrations between our core applications, identity providers and data security platforms.

What You Will Do

• Own deliveries and features from start to finish

• Design, build, and own backend services in a microservices-based, event-driven architecture

• Implement core domain logic that drives key product workflows and system behavior

• Ingest and process high-volume usage and event data from customer-facing endpoints

• Build backend services that support operational, analytics, and reporting use cases

• Model, persist, and manage domain data, enabling querying, filtering, and lifecycle management

• Expose well-designed APIs and webhooks consumed by customers, UIs, and external systems

• Power customer-facing UI experiences by providing backend APIs for visibility, analytics, and configuration

What You Bring

• 3–5+ years of professional software engineering experience building backend services and distributed systems in the Java ecosystem (Java, Spring Boot, Maven/Gradle)

• Strong understanding of event-driven architectures, asynchronous processing patterns, messaging systems, and distributed system design

• Proven experience designing and maintaining RESTful APIs, web hooks, and service-to-service integrations

• Comfortable operating in AWS, GCP, or Azure environments and working with modern observability tooling, logging, and monitoring platforms

• A track record of delivering performant, reliable and scalable applications

• Excellent collaboration and communication skills in cross-functional teams

You Might Be a Fit if You

• Have experience building products in cybersecurity, identity, governance, compliance, data protection, or enterprise SaaS environments

• You understand not just how to build systems, but why architectural decisions matter

• You can balance scalability, reliability, maintainability, and speed of execution

• You think critically about security, observability, and operational excellence from day one

• Love the idea of blending software development, distributed systems and data-intensive applications

• Strong familiarity with authentication and identity technologies such as OAuth, OpenID Connect (OIDC), SAML, SCIM, Entra ID (Azure AD), Okta, or other enterprise identity providers

• Thrive in fast-paced startup environments where ambiguity is the norm

• Enjoy shaping culture and engineering practices, not just writing code

• Leverage AI tools as an engineer 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’re 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 off-sites (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 embrace new, unfamiliar situations that require initiative and rapid decision-making. We orient ourselves quickly and deliver results with minimal guidance.

🔥 Never Full

We raise our hands, take on challenges, and assist others whenever possible. We hunger for opportunities to learn and do more.

🤝 Perfect Harmony

We support one another to create cohesion and unity. We collaborate openly, share feedback honestly, and help everyone produce their best work