Staff/Principal Fullstack Software Engineer

Witness AI•Mountain View, CA

2d•$216,000 - $274,000•Hybrid

About The Position

WitnessAI is hiring a Staff/Principal Fullstack Software Engineer for an individual contributor role with org-wide scope. The role partners closely with the Head of Product Engineering on technical strategy and engineering growth, and owns the end-to-end architecture of the web platform customers use to see, control, and secure AI activity across their companies. The work spans the React UI, APIs, Go/Rust services, and data stores. The engineer remains hands-on, shipping code while leading technical work across the stack and raising engineering standards through design reviews, mentoring, and example. The position will set technical direction for the product application, deliver features from initial concept through production release, and improve the platform’s scalability, performance, reliability, and usability. It includes collaborating with product, design, platform, and security teams, as well as advocating for an AI-native software and product development lifecycle and associated tooling. The role is based in Mountain View, California, with a hybrid schedule requiring two days per week in the office. The salary range is $216,000–$274,000, with the exact amount determined by location, qualifications, experience, and relevant skills.

Requirements

At least 10 years of experience building production web applications.
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, Remix, or another server-rendered full-stack framework.
Production experience with Go or a comparable language.
Experience building services and REST or GraphQL APIs.
Solid SQL and data modeling skills.
Experience designing multi-tenant SaaS.
Working knowledge of Docker and Kubernetes.
Working knowledge of CI/CD pipelines.
Demonstrated mastery of architecture design, enterprise scalability, and cross-domain technology stacks.

Nice To Haves

Experience owning a platform that was designed, operated in production, and maintained over several years.
Ability to work effectively across both user interfaces and backend services.
Experience building for enterprise customers, including role-based access, audit logs, and tenant isolation.
Experience writing clear design documents and architecture decision records.
Experience shipping with LLM APIs or AI-assisted tooling, and a considered perspective on where these tools are useful.
Startup experience and comfort working with unclear scope and changing priorities.

Responsibilities

Design and own the end-to-end architecture of the product application, including the frontend, APIs, services, and data model.
Write architecture decision records for major technical decisions and guide those decisions through production implementation.
Build and ship features using full-stack TypeScript with React Router, as well as Rust and Go services.
Take features from an initial idea through to a running release.
Define stable API contracts and schemas as the platform and customer base grow.
Own multi-tenant concerns, including isolation, performance, and migrations.
Identify and resolve bottlenecks in page-load time, query time, and service latency.
Set standards for testing, observability, and release safety.
Work with product and design to make complex security and policy data understandable through dashboards and workflows.
Lead design reviews and review code across teams.
Mentor senior and mid-level engineers and settle technical disagreements through clear reasoning.
Partner with product, design, platform, and security engineers to plan and deliver cross-team work.
Break large projects into work others can take on.
Advocate for an AI-native software development and product development lifecycle and associated tooling.