Lead Security Engineer

Harrison Clarke; San Francisco (CA); On-site; USD 250,000 - 350,000; Full time

Job summary

Harrison Clarke is partnering with a high-growth AI company to hire its first dedicated security leader. This is a true 0 to 1 security role, defining and building the function from the ground up while remaining deeply hands-on across security engineering, cloud, identity, apps, and AI-specific threats.

You’ll own strategy, architecture, threat modeling, and incident readiness, partnering with engineering and leadership.

Qualifications

• 8+ years in security engineering, product security, infra security or related fields.
• Hands-on engineering background required; not purely managerial.
• Experience as first or early security hire in a startup.
• Strong coding ability in Python, Go or similar.
• Deep expertise in at least one security domain with breadth as a generalist.
• Solid understanding of cloud infrastructure, identity, app security, and modern dev environments.
• Offensive security mindset through red teaming, pentesting, or adversarial testing.
• Genuine interest in AI security and emergent threats.
• Ability to work autonomously and solve novel problems.
• Excellent communication with engineers and leadership.

Responsibilities

• Build the security function from ground up: strategy, architecture, roadmap, tooling, implementation.
• Design and implement security across cloud, IAM, endpoints, apps, and internal systems.
• Establish security standards and controls with minimal friction for engineering teams.
• Develop threat models for AI/ML systems and infra surfaces.
• Partner with engineering on architecture reviews, threat modeling, testing, and improvements.
• Hands-on security engineering, including coding and internal tooling when appropriate.
• Manage external security/IT partners and decide what to bring in-house.
• Lay foundations for SOC 2, ISO 27001, and future compliance initiatives.
• Own incident preparedness, detection, response, and post-incident improvements.
• Help shape long-term security org and build a small, highly technical team.

Skills

Hands-on engineering

Python or Go

Cloud security

Threat modeling

Security leadership

Security architecture

Communication with leadership

Tools

Cloud tooling

Job description

Harrison Clarke is partnering with a highly ambitious, well-funded AI company to hire its first dedicated security leader.

This is a true 0 to 1 security role. You’ll have the opportunity to define and build the security function from the ground up, while remaining deeply hands‑on across security engineering, cloud infrastructure, application security, identity, corporate security, and emerging AI-specific threats.

What You’ll Own

• Build the security function from the ground up, including strategy, architecture, roadmap, tooling, and implementation
• Design and implement security across cloud infrastructure, identity and access management, endpoints, applications, and internal systems
• Establish security standards and controls without introducing unnecessary friction for engineering teams
• Develop threat models for complex AI and ML systems, infrastructure, and emerging attack surfaces
• Partner closely with engineering teams on architecture reviews, threat modeling, adversarial testing, and security improvements
• Take a hands‑on approach to security engineering, including writing code and building internal tooling where appropriate
• Manage existing external security and IT partners while determining which capabilities should be brought in-house
• Establish the foundations required for future compliance initiatives such as SOC 2 and ISO 27001
• Own security incident preparedness, detection, response, and post‑incident improvement
• Help shape the long‑term security organization and eventually hire and develop a small, highly technical team

What We’re Looking For

• 8+ years of experience across security engineering, product security, infrastructure security, offensive security, or related disciplines
• A strong hands‑on engineering background - this is not a purely managerial or governance‑focused position
• Experience operating as the first or an early security hire, or significant experience building security capabilities in an early‑stage environment
• Strong coding ability, ideally with Python, Go, or another systems/backend language
• Deep expertise in at least one security domain, combined with the breadth and curiosity to operate as a security generalist
• Strong understanding of cloud infrastructure, identity, application security, and modern software development environments
• An offensive security mindset, developed through areas such as red teaming, penetration testing, vulnerability research, security consulting, or adversarial testing
• Genuine interest in AI and the emerging security challenges associated with increasingly capable AI systems
• Comfortable operating with significant autonomy and solving problems where established playbooks may not yet exist
• Strong communication skills and the ability to work directly with engineers and company leadership