Senior Fullstack Engineer

Senior Fullstack Engineer

Foresite is seeking a product-minded Senior Fullstack Engineer with a mastery of modern front-end architectures to help build and scale our multi-tenant SaaS platform. As a foundational member of our engineering team, you won't just write code—you will architect the "humans-first" interfaces that make complex cybersecurity data intuitive and actionable.

What You'll Do

In this role, you'll be working on our multi-tenant SaaS platform built with modern web technologies. Your primary focus will be leading the evolution of our front-end ecosystem while maintaining a strong, lateral grip on our backend services. You will ensure our platform remains performant, accessible, and maintainable as we scale.

• Architect and build front-end features for our multi-tenant SaaS platform using React.js and TypeScript
• Work across the full stack, owning backend integrations and data access patterns end-to-end
• Build and maintain a shared component library that scales consistently across our client base
• Partner closely with product, design, and backend engineers to ship polished, production-ready features
• Integrate with PostgreSQL and NoSQL data stores through clean, well-structured backend service layers
• Design, consume, and extend RESTful APIs that power our platform's core workflows
• Champion code quality through thorough reviews and consistent enforcement of engineering standards
• Own your deployments—debugging, performance tuning, and keeping production healthy
• Drive architectural decisions and contribute to engineering roadmap planning
• Mentor junior and mid-level engineers through pairing, feedback, and code review
• Identify and address performance bottlenecks across the front-end and API layers
• Apply security-conscious development practices, particularly around auth, RBAC, and data isolation in a multi-tenant context
• Engage actively in Agile ceremonies including sprint planning, standups, reviews, and retrospectives
• Document what you build and contribute to a culture of knowledge sharing across the team

Who You Are

• Experience: 5+ years of professional experience in Full Stack development, with a clear specialization in front-end architecture for complex B2B SaaS or Cybersecurity platforms.
• The Modern Stack: You are deeply proficient in React 18/19 and TypeScript. You are comfortable with React Router v7 and modern routing patterns.
• Web Security: You build secure web applications by default. You understand and mitigate common vulnerabilities such as XSS, CSRF, and injection attacks, and know how they apply in modern React and TypeScript apps.
• Data & Backend: You are comfortable designing schemas, writing queries, and reasoning about performance across PostgreSQL and Firestore. You feel at home with modern ORMs and use runtime validation to enforce data integrity at system boundaries.
• Architectural Foresight: You have experience with multi-tenant architectures and implementing robust RBAC/ABAC models to enforce strict data isolation.
• Reliability as a Habit: You write tests as part of the job, not as an afterthought. You are proficient with Vitest and Testing Library for unit and integration coverage, and Playwright for critical E2E flows.
• Tooling & Workflow: You care about developer experience. You are comfortable with CI/CD pipelines, Git, and modern workflows like Stacked PRs. You embrace AI-assisted development tools to ship faster without sacrificing quality.
• Integration Expert: You are comfortable on both sides of a system boundary—consuming third-party APIs on the frontend and writing the backend glue that connects them. You understand API contracts, webhook reliability, and data consistency across services.

Nice to Have

• You have a background in Cybersecurity, understanding the unique UI/UX and security challenges of the industry.
• You have a "Security First" approach to coding, always thinking about the OWASP Top 10.

Why Join Foresite?

We are a mission-driven partner helping organizations navigate an increasingly complex threat landscape. Founded by security practitioners, we've grown into a global leader in SecOps and MDR by staying true to our core value: radical transparency. When you join Foresite, you are part of a "humans-first" culture where your expertise is valued, and your well-being is a priority. We leverage our Google Cloud Premier SecOps Partnership to stay at the cutting edge, but we know that our greatest asset is our people.