Security Engineer

Saturn is a Series A-backed fintech transforming how financial advice is delivered. We operate in one of the world’s largest industries. Wealth and asset managers oversee more than $100 trillion and generate over $1 trillion in annual revenue, yet much of the infrastructure used to manage that wealth remains fragmented, manual and institution-specific. Saturn is starting with the productivity and compliance systems used by financial advisers.

Saturn joined Y Combinator in 2024 and became one of the fastest-growing B2B companies in its batch. We grew organically to a meaningful share of the UK financial advice market before acquiring the legacy leader, one of the industry’s most established compliance rule engine and suitability businesses, in 2025. That acquisition combined AI-native product engineering with more than two decades of regulatory expertise, proprietary compliance logic and deep industry distribution. Within two years of launch, Saturn became the leading provider of AI transformation to UK financial advice firms, supporting more than 9,000 regulated advice professionals who manage about $500bn in assets. We have proved distribution, trust and demand. The most important infrastructure is still ahead of us.

Your role as a Security Engineer involves owning the security of the systems financial institutions trust with sensitive client data and regulated financial workflows: our applications, our cloud infrastructure and the engineering practices that produce them. You will not operate as a gatekeeper or arrive at the end of a project to review it. You are expected to understand how systems actually work, identify where a failure or an attack would cause real harm, and help teams fix it at the right level. Your work is what allows Saturn to meet the security expectations of large financial institutions without slowing engineering down with process for its own sake.

The Team consists of engineers who care deeply about craft, speed and quality. They include early and founding team members from companies including Rippling, Postman, Gojek, CRED and Slice. You will work alongside product designers, backend engineers, AI engineers and domain experts with decades of experience in financial advice and compliance. We are building a small, high calibre engineering organisation for people who want genuine ownership, difficult product problems and the opportunity to shape an important company while its foundations are still being formed.

What You’ll Work On:

• Application and API security across Saturn’s web applications, backend services and integrations, including authentication, authorisation, session management and firm-level data separation.
• AWS security, covering IAM, network controls, secrets, encryption and workload isolation.
• Threat modelling and security review for new systems, financial workflows, external integrations and AI capabilities, joining projects early enough to change their design.
• Vulnerability management end to end: discovery, prioritisation by real risk, remediation and verification across code, dependencies, cloud resources and employee systems.
• Security tooling and automation, including checks built into CI/CD, so the same work is never done manually twice.
• Detection and incident response, from logging and alerting through investigation and recovery, turning each incident into a lasting improvement to systems and controls.
• AI security, including prompt injection, unsafe tool execution, retrieved data and sensitive information disclosure.
• Evidence and assurance for SOC 2, enterprise security reviews and customer due diligence, plus the reusable security patterns engineering teams adopt as standard.

What We’re Looking For:

• Security engineering experience. 3+ years in security engineering, software engineering, infrastructure security or a closely related role, with a track record of improving the security of production software or cloud infrastructure.
• Application and API security depth. Strong command of common web and API vulnerabilities including the OWASP Top 10, and practical knowledge of authentication, authorisation, sessions, secrets and encryption.
• Cloud security. Hands-on experience securing AWS or another major cloud platform, including IAM, network security and cloud-native controls.
• Secure design. You have run threat modelling and architecture reviews, and you recommend proportionate controls that fit the system and its stage rather than the textbook answer.
• You build, not just advise. You can write software and automation in Go, TypeScript, Python or a comparable language, and you integrate security checks into how engineers already work.
• Detection and response. Understanding of security logging, monitoring and incident investigation, and comfort owning a problem through investigation, remediation and verification.
• Risk judgement at startup pace. You start from the likely harm and attack path, separate material risk from low-value security work, and prioritise sensibly with incomplete information.
• Strong written communication. You describe risks and mitigations clearly enough that engineers, customers and leadership can act on them, and you document accepted risks rather than leaving them implicit.

Preferred:

• Security engineering in financial services or another regulated domain.
• Application or product security for a B2B SaaS platform, including data isolation in multi-tenant systems.
• AWS security services, infrastructure as code, and enterprise identity integrations such as OAuth, OIDC and SAML.
• Detection engineering, SIEM or cloud security monitoring, incident response or digital forensics.
• SOC 2, ISO 27001 or enterprise customer security reviews.
• Penetration testing or working with external security researchers.

What We Offer:

• Competitive salary with regular appraisals.
• Competitive equity package at an early stage company with high growth potential.
• Our beautiful new five-floor office, “The Dome”, equipped with an onsite gym and roof terrace.
• Best-in-class dental and medical insurance.
• A dedicated budget for learning and professional development.
• Access to an additional world-class gym and wellness centre two minutes from the office.
• A tight-knit, ambitious team that cares deeply about quality and each other.