Senior Frontend React Developer

About Shelf

The enterprise is going agentic and we are creating a unique operating system for an automated future.

Most AI agents break the moment they hit real business complexity. That’s why we built a platform that models a company's policies, workflows, and operational logic into an AI Data Model. Shelf enables AI Agents to reliably reason and deliver precise and reliable outcomes at scale.

We already have what most AI startups are still trying to earn: Enterprise customers such as Glovo, Nespresso, and HelloFresh, real production data, and tens of thousands of users. Customers trust us with operational knowledge: Our platform is highly reliable and secure with SOC2, HIPAA-ready security practices, and mature integrations in place.

Location - Warsaw, work from the office.

Senior Frontend React Developer

This role is for a senior frontend engineer who can design and own business-critical user experiences for agentic AI products.

We want someone who is strong technically, has strong UI judgment, communicates clearly, and has the taste to make complex product experiences simpler, faster, more trustworthy, and easier to evolve over time. Expect real ownership from frontend architecture through production quality. You will build production Next.js applications with complex state, real-time AI interactions, and multiple layers of enterprise functionality.

The team is small enough for engineers to make real decisions. Career growth comes from ownership. Titles matter less than the scope you can carry. The people who grow fastest take responsibility for larger product surfaces, drive customer outcomes, and strive to develop better engineering practices.

You solve ambiguous frontend problems by understanding the user need, shaping the right interaction model, then shipping, iterating, and keeping the experience healthy in production.

We build AI-native. Engineers use Codex, Claude Code, and agents they build themselves. We invest in harness engineering through skills, CLIs, logs, traces, and orchestration.

This is a role for someone in a high-growth chapter of their career, who wants to do the best work of their life, learn fast, and win as part of a team going all-in on a hard mission.

What You Will Own

• Design and ship production Next.js SSR applications with complex state, high-load scenarios, and real-time AI interactions at scale
• Build interfaces for AI-powered features: streaming LLM responses, semantic search across millions of documents, interactive knowledge graphs, and agentic builders
• Architect component libraries and maintain the design system, ensuring reusability, accessibility, and consistent UX across the platform
• Deliver enterprise-grade functionality: localization, accessibility compliance, cross-browser support, and security
• Take full ownership after launch: monitor performance in production, optimize bundle sizes, instrument for Core Web Vitals, and ensure things scale gracefully
• Keep the bar high on code quality, testing, and craft through thoughtful code review and mentorship

What Strong Performance Looks Like

• You turn vague product problems into shipped, well-reasoned interfaces that users trust
• Complex AI behavior feels legible and controllable to users because of how you built the UI
• Your components are reusable, accessible, and fast under real enterprise load
• You bring momentum. Work moves because you are on it

What We Are Looking For

• Over 5 years of frontend engineering experience, including 3+ years specializing in React and modern TypeScript
• Production Next.js experience: SSR applications at scale, app router, server components, and the trade-offs between SSR, SSG, and CSR
• Complex state management for hard scenarios: real-time collaboration, optimistic updates, multi-tenant isolation, large-scale data sync
• Experience building AI/LLM interfaces: streaming token responses, chat UIs, semantic search, or similar real-time AI interactions
• High-load performance work: you monitor Core Web Vitals and know how to improve them under heavy traffic and large datasets
• Enterprise application depth: localization, accessibility, security, and compliance, you understand the complexity beyond "making it work"
• A security-conscious approach to engineering: you handle sensitive data carefully and think about the security implications of what you ship
• Strong craft and product instinct: you don't wait for perfect designs, you spot UX issues and propose solutions, and you're never satisfied with "good enough"
• AI-native working style. You already use AI coding agents daily and are eager to push the boundaries of harness engineering
• Clear communication. You articulate design decisions and technical trade-offs clearly, verbally and in writing

Strong Plus

• Experience with React Flow, Highcharts, or other complex data-visualization libraries
• Hands-on experience with vector search UIs, RAG interfaces, or generative UI
• Understanding of Node.js/Python: you can read backend code and contribute to API design discussions
• Built or contributed to design systems or open-source component libraries

How We Evaluate Fit

We care more about craft, ownership, and the ability to make complex AI feel trustworthy than a perfect match to every library on paper. If you are the kind of engineer who can take a messy, complex enterprise problem and turn it into an interface people trust, we want to talk.

Why Shelf

• Becoming one of the defining companies of the AI age is a hard plan, and our leadership team has the rare mix of deep AI, knowledge-management, and enterprise SaaS experience to actually execute it
• We have raised over $60 million in funding; our investors include Tiger Global, Insight Partners, Base10, and others
• Recognized by Gartner as a Cool Vendor, with high-velocity growth powered by the most innovative product in our category
• We love our customers and our customers love us. Ask a Shelf customer why, and they'll tell you it's our innovative capabilities and rock-solid reliability, that they enjoy working with our people, and most of all, the improvements they see in their business KPIs
• We're building fast across three hubs: our New York HQ and our Product and Engineering centers in Warsaw and Lviv