Senior Frontend Full Stack Engineer at Complexio

Location: Warsaw, Masovian Voivodeship
Type: Full-time
Level: Senior
Posted: Dec 2, 2025

Description

Complexio is seeking a Senior Frontend Full Stack Engineer to join their team. The company is building an intelligence layer for enterprise AI, focusing on real-time automation and insight through an Event Knowledge Graph and AI models. The role involves shaping user engagement with the platform, crafting web applications and user experiences, and translating data-rich insights into intuitive interfaces. The ideal candidate is passionate about front-end engineering, full-stack product delivery, and enterprise AI innovation, thriving in a fast-moving, technical environment.

Required Skills

React
TypeScript
JavaScript
Vite
ESLint
REST APIs
LLM
Vitest
Jest
React Testing Library
UX
Python
FastAPI
Electron
React Query
Zustand
Node.js

Additional Information

Required Previous Experiences: advanced React + TypeScript
Strong JavaScript fundamentals (async, modules, performance)
Experience with Vite, ESLint, modern tooling
Building scalable UI with components, hooks, and context
Integrating with REST APIs, async flows, error handling
Writing maintainable code + strong code review skills
Familiar with LLM-based features (streaming, prompts, AI-driven UI)
Testing with Vitest/Jest + React Testing Library
Good UX instincts & ability to work independently
Python backend familiarity (FastAPI/async I/O, API contracts)
Preferred Qualifications: Experience with Electron apps (main/renderer, preload, IPC)
React Query / Zustand or other state libraries
Advanced TypeScript patterns (generics, mapped types)
Performance debugging (React Profiler, bundle optimization)
Knowledge of Radix/shadcn/ui or similar component libraries
Node.js fundamentals
Event- driven systems familiarity

About Complexio

Complexio

Enterprise AI

Complexio connects data, people, and systems into an intelligence layer for enterprise AI, where users can ask questions in natural language and get answers from real operational data. It turns live interactions into a living blueprint of a business, using an Event Knowledge Graph to map how work happens in real time.