Senior Full-Stack Engineer

Senior Full-Stack Engineer Legitmark is building the trust layer for resale. We believe that authentication should be fast, accurate, and accessible to everyone, from individual sellers to the world's largest marketplaces. Our team of experts and engineers authenticate millions of items annually, helping buyers shop with confidence and sellers maximize value. As a Senior Full-Stack Engineer, you'll work across our entire stack to build features that directly impact how sellers and buyers experience authentication. This role combines deep technical work with product thinking. You'll shape not just how we build, but what we build. This is a high-ownership role. We're a small team moving fast, which means you'll take features from idea to production with minimal handoffs. We expect you to leverage modern AI-assisted development tools to ship quickly and maintain high quality. This role is remote-first with flexible hours. We work asynchronously across time zones and value output over presence. In this role, you'll: Build and maintain core authentication platform features end-to-end Design and implement APIs that scale to millions of requests daily Collaborate with product and authentication experts to ship user-facing features Improve system reliability, performance, and observability Contribute to technical decisions and help shape engineering culture Integrate AI/ML components into production authentication workflows We're an AI-native engineering team. We use Cursor with Claude as our primary development tools and expect engineers to be proficient with AI-assisted workflows. That includes debugging, code generation, refactoring, and rapid prototyping. If you're still writing every line manually, this probably isn't the right fit. This doesn't mean we want prompt-and-pray engineers. You need deep technical fundamentals to know when the AI is wrong, architect systems correctly, and debug complex production issues. AI tools make good engineers faster; they don't replace engineering judgment. Your first 90 days Day 30: First features in production. You're set up across our stack, shipping to real users, and comfortable with our AI-assisted workflows. Day 60: Owning a surface. You've taken a core area of the platform end-to-end — from design through deploy — with minimal handoffs. Day 90: Raising the bar. You're driving technical decisions, improving reliability or performance in a measurable way, and shaping how we build. We're looking for someone with: 5+ years of experience in full-stack development Proficiency in TypeScript, React, and Node.js Experience building and scaling production systems Strong fluency with AI-assisted development tools (Cursor, Claude, or similar) Ability to debug effectively across the full stack, including AI-assisted debugging workflows Strong communication skills and ability to work asynchronously Comfort with ambiguity and a bias toward action Nice to have: Experience with MCP (Model Context Protocol) and agentic tooling patterns Background integrating AI/ML models into production applications Familiarity with authentication, fraud detection, or trust & safety systems Experience with Orkes or workflow orchestration platforms You might thrive in this role if: You're a builder. You enjoy taking problems from zero to one and iterating quickly based on feedback. You're AI-native. You've internalized AI tools into your workflow and can't imagine going back. You're customer-focused. You think about the user experience in everything you build and care about the details. You push your peers. You proactively contribute ideas, challenge assumptions, and help us move faster. Legitmark is an authentication services company that verifies luxury goods and sneakers for the world's largest resale platforms. Our human-powered approach delivers 98-99% accuracy with industry-leading turnaround times, serving over 125,000 businesses globally. We are an equal opportunity employer. Legitmark