Senior Security Engineer - Primer

An Introduction to Primer

Primer is the unified infrastructure for global payments. We give finance and payments teams the visibility and control to reduce complexity, improve performance, and capture more revenue - all from a single platform.

Which team will you be joining?

You'll be joining the ProdSec/AppSec team to help build the entire product security surface for a company processing payments at scale: threat modelling, security review, compliance, incident escalation, and the multi-year AppSec roadmap. You'd be the second hire, and the function that function finally gets to share the work with.

This is a hands-on delivery role, and a genuinely formative one. You'll help set the security strategy and architecture; you take real ownership of the work that turns it into reality, reviews, research, automation, and the day-to-day partnership with engineering teams.

What will you be doing?

• Running security reviews and threat modelling on features and systems across Primer's product, and turning findings into clear, actionable guidance
• Independently planning and delivering your own security projects, from initial design through to rollout
• Building tooling and automation that makes future reviews faster and cheaper to run
• Coordinating penetration testing and tracking remediation through to closure
• Supporting recurring compliance work (SOC2, PCI), including evidence collection and remediation tracking
• Contributing to AppSec roadmap initiatives across application threats, AI security, supply chain security, and ASPM
• Picking up proactive security work, threat research and hands-on investigation
• Working alongside Cloud, Infra, and GRC on the security aspects of their projects

What we're looking for

• Working experience in product or application security: security reviews or threat modelling and spotting risks that matter
• Ability to read and write code, not just review it. Comfortable building small tools and automation
• Sound judgement about risk and the ability to explain reasoning clearly
• Ability to plan and deliver work independently
• Clear communication with engineers who aren't security specialists

Nice to have:

• Exposure to compliance frameworks like SOC2 or PCI
• Background in payments, fintech, or another regulated, high-stakes domain
• Interest in supply chain security, detection engineering, or AI security

Benefits

• Fully remote and globally distributed team
• Competitive share options
• Uncapped holiday (25 days minimum)
• Co-working space access across major cities
• Workations & Company Retreat
• £500 towards home office setup
• Generous learning budget
• Private Medical Insurance