You will join an elite team building the foundational endpoint agent for a category-defining AI security platform. Using Rust, you will develop high-performance, low-level software that protects sensitive data in real-time across Windows, macOS, and Linux. This role is critical in enabling enterprises to adopt AI tools safely at scale.
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London, United Kingdom£150k–£195k + Equity
Systems Engineer at $25M Series A AI security startup
Join a category-defining Series A cybersecurity startup backed by Next47 and Ten Eleven Ventures as they build the security layer for the AI era. As a Systems Engineer, you will own the low-level Rust architecture for endpoint agents that protect sensitive data in real-time across millions of devices. With a veteran founding team and £150k–£195k base salary plus meaningful equity, this is a rare opportunity to shape foundational security technology for the next decade of enterprise AI adoption.
Overview
Role overview
Company
Harmonic Security Inc.
$25M Series A cybersecurity startup backed by Next47, Ten Eleven Ventures, and In-Q-Tel
Responsibilities
What you will do
- Design and optimize security agent components in Rust, ensuring sub-500ms inference and zero-touch data protection on user devices.
- Conduct technical research to implement cross-platform signals and controls for data movement across Windows, macOS, and Linux subsystems.
- Build robust, CI-tested deployment mechanisms for client-facing releases that maintain high reliability and performance under real-world conditions.
Candidate profile
Who this is a fit for
- Deep production experience in Rust or C++ with a strong focus on systems programming concepts like memory safety, concurrency, and IPC.
- Proven track record building security-critical client software such as endpoint agents, EDR/XDR components, or low-level OS utilities.
- AI-forward mindset with the ability to leverage modern tools like Claude Code or Cursor to accelerate high-expertise systems development.
What makes it remarkable
Why this role is remarkable
- Work at the bleeding edge of AI governance, building the security layer for a world where every enterprise employee uses an AI copilot.
- Join a high-traction startup led by experienced founders who previously scaled Digital Shadows, supported by top-tier investors like In-Q-Tel and Next47.
- Total ownership over core architecture with a highly technical team that values Rust, memory safety, and high-performance systems engineering.
Jack & Jill
How Jack & Jill work together
I get to know what you’re great at, then find roles you’d never find yourself.Ok, I'll go first. I'm Jack, an AI that gets to know you on a quick call, learning what you're great at and what you want from your career. Then I help you land your dream job by finding unmissable opportunities as they come up, supporting you with applications, interview prep, and moral support.
I recruit from Jack’s network and make the intro when I spot a great match.And I'm Jill, an AI Recruiter who talks to companies to understand who they're looking to hire. Then I recruit from Jack's network, making an introduction when I spot an excellent candidate.
Meet Jack
Jack gets to know what you're great at and what you want next, then searches 14 million jobs daily and introduces you directly to hiring managers.
How does this work?
Jack's an AI agent for job searching and career coaching. He works for you.
Jill is the AI recruiter working for the company. She recruits from Jack's network.
If it's a match and the company wants to meet you, they'll make the intro. In the meantime, if you'd like, Jack will send you excellent alternatives.
Jack