Staff/Principal Fullstack Software Engineer

Staff/Principal Fullstack Software Engineer Location: Mountain View, CA | Hybrid, 2 days/week in office

About Us: WitnessAI is the unified AI security and governance platform enterprises trust to govern and protect all AI activity. We provide complete, network-level visibility into every interaction including employees and autonomous agents, even in native apps where legacy tools are blind. Unlike security that relies on outdated keywords, our platform understands intent, enabling intelligent policies that stop novel threats like prompt injection while empowering productivity. WitnessAI transforms security from a bottleneck into the enabler of your AI strategy as the confidence layer for enterprise AI. The Role This is a Staff/Principal role with org-wide scope. You’ll work hand in hand with the Head of Product Engineering on technical strategy and help grow the engineers around you. That work centers on our web platform, which customers rely on to see, control, and secure AI activity across their company. You’ll shape its architecture end to end, from the React UI to the Go/Rust services and data stores behind it. This is an individual contributor role, and you’ll be in good company: nobody here has stopped coding. We all ship code every day alongside our AI Agents, which feels fitting to a team whose job is keeping AI in check. You’ll lead technical work across the stack, from the UI to the ingress pipeline and raise the engineering bar through design reviews, mentoring, and the example you set in your own code. What You'll Do

• Architecture. Design and own the end-to-end architecture of the product application: frontend, APIs, services, and data model. Write ADRs for the big decisions and see them through to production.

• Build across the stack. Ship features in full-stack TypeScript (React Router), Rust and Go services. Take a feature from a rough idea to a running release.

• API and data design. Define API contracts and schemas that stay stable as the platform and customer base grow. Own multi-tenant concerns like isolation, performance, and migrations.

• Performance and reliability. Find and fix bottlenecks in page load, query time, and service latency. Set standards for testing, observability, and release safety.

• Make complex data usable. Work with product and design to turn dense security and policy data into dashboards and workflows that a busy admin can understand in seconds.

• Technical leadership. Lead design reviews, review code across teams, and mentor senior and mid-level engineers. Settle technical disagreements with clear reasoning.

• Cross-team work. Partner with product, design, platform, and security engineers to plan and deliver work that spans teams. Break large projects into pieces others can pick up.

• Hands-on AI work. Be an advocate for building an AI native SDLC and PDLC with associated tooling.

What We're Looking For

• 10+ years building production web applications, with at least 3 years in a senior, staff, or principal technical leadership role.

• Deep experience with TypeScript, React, and Node.js. Experience with React Router or Remix, or another server-rendered full-stack framework.

• Strong backend skills. Production experience with Go or a comparable language, and with building services and REST or GraphQL APIs.

• Solid SQL and data modeling skills. Experience designing for multi-tenant SaaS.

• Working knowledge of Docker and Kubernetes, and of CI/CD pipelines.

• Demonstrated mastery in architecture design, enterprise scalability, and cross-domain tech stacks.

What Will Make You a Stellar Candidate

• You have owned a platform, not just features. You can point to a system you designed, ran in production, and lived with for years, including the parts you would change.

• You are equally good at the UI and the service behind it. You care about what a user sees and about what happens to the request after they click.

• You have built for enterprise customers. You know what role-based access, audit logs, and tenant isolation require, and you plan for them early.

• You write things down. Your design docs and ADRs are clear enough that someone new can follow the reasoning a year later.

• You have shipped with LLM APIs or AI-assisted tooling. You have a view on where it helps and where it does not.

• You have worked in a startup. You are comfortable with unclear scope and changing priorities, and you pick a direction and move.

Why This Role

• You set the technical direction for the product application at a company growing fast in AI security.

• Enterprise customers use what you build to govern real AI activity, so the work matters from day one.

• You work directly with product, design, and the CEO's leadership team, with few layers between you and the decision.

• The problems are new. AI security has no settled playbook, and you help write it.

Benefits:

• Hybrid work environment

• Competitive salary and equity

• Health, dental, and vision insurance

• 401(k) plan

• Opportunities for professional development and growth

• Generous vacation policy

Salary: $216,000 - $274,000 (The exact salary will be determined based on the selected candidate’s location, qualifications, experience, and relevant skills.)