Frontend Product Engineer for AI UIs (React/TypeScript) – Amsterdam

MarvelX AI; Amsterdam; Hybrid; EUR 70,000 - 110,000; Full time

Job summary

MarvelX AI in Amsterdam is seeking a Product Engineer (Frontend leaning) to own user-facing surfaces for our AI agents, turning complex AI behavior into calm, trustworthy interfaces for regulated industries. You will design and build features in React and TypeScript, create responsive UIs, and handle real-time streaming interfaces.

You’ll also collaborate on backend slices with Python/FastAPI and help define API contracts.

Qualifications

• Two to five years building production React applications with TypeScript.
• Deep understanding of React patterns, hooks, rendering lifecycle, and state management.
• Strong CSS skills (Tailwind, CSS-in-JS, or strong vanilla CSS) and responsive design instincts.
• Comfort owning a feature end to end, including the backend slice that supports it.
• Willingness and ability to work across the stack, backend included, when the feature needs it.
• Product sense: you reason about the user and the outcome, not only the code.
• Strong testing instincts (unit, integration, E2E).
• Experience building UIs for B2B / enterprise customers (data tables, role-based views, multi-tenant dashboards).
• Component library or design system contribution.
• BYOC / on-prem product experience (offline-capable UIs, environment-specific config).
• Previous startup experience and comfort in fast moving environments.

Responsibilities

• Design and build user-facing features in React and TypeScript.
• Create responsive, accessible UIs that hold up against real production data.
• Build real-time interfaces for streaming AI output (WebSocket, SSE).
• Build the backend slice that feeds your interface, in Python and FastAPI, with the team.
• Integrate with backend APIs, handling loading, error, and optimistic update states cleanly.
• Diagnose and fix performance issues, perceived and measured (LCP, TTI, bundle size).
• Contribute to or help establish the component library and design system.

Skills

React

TypeScript

Frontend development

CSS

Testing

Product sense

B2B UI

API integration

Tools

Python

FastAPI

Job description

MarvelX AI in Amsterdam is seeking a Product Engineer (Frontend leaning) to own user-facing surfaces for our AI agents, turning complex AI behavior into calm, trustworthy interfaces for regulated industries. You will design and build features in React and TypeScript, create responsive UIs, and handle real-time streaming interfaces.

You’ll also collaborate on backend slices with Python/FastAPI and help define API contracts.