Senior Software Security Engineer

Harmonic Security; Greater London; On-site; GBP 110,000 - 150,000; Full time

Benefits offered by this job

401K/pension

Generous PTO

Equity

Job summary

Harmonic Security is seeking a Senior Software Security Engineer to own our platform security architecture and write the code that embodies secure design. You will shape authentication, encryption, secrets management, and multi-tenant isolation, while extending patterns across the core platform.

This is hands-on work in a fast-moving environment. You will collaborate with the platform team, manage your security backlog, and run threat modeling to ensure security is built in from the start.

Qualifications

• 6+ years of hands-on software engineering with deep specialization in security architecture.
• Experience building secure-by-design systems and setting technical standards.

Responsibilities

• Take formal ownership of Harmonic's platform security architecture (authentication/authorization, secrets management, encryption, multi-tenant isolation).
• Write production code to harden and extend security patterns in the core platform using Java, Terraform, TypeScript, Rust or Python.
• Collaborate with platform engineering to weave security into the shared framework and architecture decisions.
• Manage your own backlog of platform security improvements, prioritized independently from product roadmap.
• Run threat modeling and architecture reviews for major new systems before they ship.
• Partner with Security team to provide evidence of compliance and beyond.

Skills

Software security architecture

Java

Terraform

OpenTofu

AWS security

Threat modeling

Security standards

Tools

Terraform

OpenTofu

AWS

Job description

AI doesn't run in one place anymore. It runs in the browser tab, the desktop app, the agent your engineers kicked off, and the copilot embedded in the tools you already pay for. Harmonic Security governs all of it. Our AI Governance and Control (AIGC) platform sits on the device, inside the interaction, at the moment of action, reading what AI is actually doing (not just the traffic around it) and acting in under 200ms. Security teams get full visibility and control across every AI surface, including the agentic and MCP layer that traditional tools can't see. Their people get to innovate without guardrails slowing them down. We're gaining serious traction at the intersection of AI and cybersecurity, and backed by investors who know the space: N47, Ten Eleven Ventures, and In-Q-Tel. As AI adoption inside the enterprise accelerates, the ability to safely observe, control, and enforce policy in real time isn't a nice-to-have. It's mission-critical infrastructure. That's what we build.

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 fast. 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 Senior Software Security Engineer to become the authority on our platform's security architecture - and to write the code that embodies it. You'll inherit a platform where the fundamentals of authentication and authorization, secrets and key management, encryption, and multi-tenant data isolation are established, and your job is to sharpen, harden, and evolve them with the depth a dedicated specialist brings that a generalist team can't. You will establish standards and enable the rest of the team to adhere to them. You'll spend the majority of your time writing production code, not producing reports on someone else's. This is deliberately not a role for someone who wants to sit on a security team finding holes in what other people have already shipped. We want someone who'd rather build the fix into the architecture in the first place - hands‑on, opinionated, and accountable for the outcome.

What You’ll Do

• Take formal ownership of Harmonic's platform security architecture - authentication and authorization, secrets and key management, encryption at rest and in transit, and multi-tenant data isolation - and evolve it beyond what a generalist engineering team has had the focus to do
• Write production code using our existing languages and tooling (primarily Java, Terraform also Typescript, Rust, Python) to harden and extends these patterns in our core platform.
• Collaborate closely with the platform team, who own our architecture and engineering standards, so that security standards are woven into that shared framework rather than sitting alongside it - you'll shape architectural decisions together, not hand requirements over the fence
• Manage your own backlog of platform security improvements, prioritized independently of the product roadmap
• Run threat modeling and architecture reviews on major new systems and integrations before they ship, so security is designed in rather than retrofitted
• Create a close partnership with the Security team to provide evidence that we are adhering to required standards and ensure they are informed where we go beyond

What You Bring

• 6+ years of hands‑on software engineering experience, with deep specialization in security architecture rather than general backend development
• Strong working knowledge of Java, and infrastructure‑as‑code using Terraform and/or OpenTofu
• Experience with AWS and its security fundamentals - IAM, network security, container and secrets management.
• Strong grounding in threat modeling and secure‑by‑design principles, applied to real architectural decisions rather than theoretical frameworks
• Comfort setting technical standards that other engineers are expected to follow, with the communication skill to bring people along rather than dictate from a distance

You Might Be a Fit if You

• Have built or hardened platform‑level security in a SaaS company that faces serious enterprise scrutiny (SOC 2, ISO 27001, customer security questionnaires, or similar)
• Would rather build the fix into the architecture than find the next hole in someone else's code
• Have no patience for security theatre - you measure success by real, shipped improvements to our security posture, not policies, paperwork, or box‑ticking that only looks like progress
• Leverage AI tools as an engineer to help you build smarter, faster and better
• Enjoy being the go‑to authority on a topic and setting the standard, rather than gatekeeping other people's work
• Are comfortable being the first specialist in this seat, inheriting a solid foundation and having the autonomy - and responsibility - to take it further
• Thrive in fast‑paced startup environments where ambiguity is the norm

Why Join Us

We're still small enough that every hire changes the company. If you're looking for a role where you can build, make decisions, and have a real impact, you'll find that here. You'll work closely with experienced leaders, help shape how we scale, and have a direct hand in building the kind of company people want to work at.

• Recognized momentum - named to Rising in Cyber 2026, a signal the market is taking notice
• Rare market opportunity - join early in a category‑defining company shaping how enterprises tackle one of tech's biggest unsolved problems
• Competitive pay and meaningful equity - a real stake in Harmonic's success, not a token gesture
• Comprehensive benefits - 401K/pension, generous PTO, flexible hybrid work
• A small, high‑trust team - transparency, creativity, continuous learning, no politics, no bureaucracy
• Thoughtful leadership that cares about your growth, not just your output
• Annual global off‑sites - past trips include Lisbon and Nashville
• Real ownership - you'll shape the platform, the culture, and the direction of the company from day one

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.