Senior Full-Stack Engineer (.NET React)

APPSTREAM STUDIO LLC; Olsztyn; On-site; PLN 218,000 - 291,000; Full time

Job summary

A leading innovation consultancy in Poland is seeking a Senior Full-Stack Engineer to lead the design and development of their AI-powered platform. You will work with a small, experienced team to enhance services and integrate cutting-edge features. Candidates should have extensive experience in .NET and React, alongside strong skills in Azure and cloud solutions. This role offers 100% remote work and opportunities for career growth.

Benefits

Remote work opportunities

Flexible working time

Integration events

Qualifications

• 5+ years of professional experience in .NET / C#.
• 3+ years of experience in React / TypeScript.
• Strong command of Azure cloud services and CI/CD pipelines.

Responsibilities

• Lead the design and development of modern full-stack applications using .NET 8, C#, and React.
• Integrate cutting-edge AI features using Semantic Kernel and GenAI APIs.
• Mentor a tight-knit team (1–2 developers), take ownership of code reviews.

Skills

.NET

C#

React

TypeScript

SQL

Azure

Tools

Entity Framework Core

GitHub Actions

Docker

Job description

Senior Full-Stack Engineer (.NET React)

Olsztyn, Warmian‑Masurian Voivodeship, Polska

Miejsce pracy: Olsztyn

Technologies we use

• .NET
• C#
• TypeScript
• React
• SQL
• Microsoft Azure

About the project

Aiventic is an AI copilot for field service professionals. It helps technicians diagnose equipment issues, identify the right parts, and perform repairs faster and more accurately. The platform combines large language models, real-world repair data, and structured service documentation to deliver guided troubleshooting and instant access to relevant technical knowledge. The goal is simple — to make every technician perform like a seasoned expert, no matter the complexity of the job.

The product is already used by service companies across the U. S. and is now entering a strong growth phase. We’re expanding integrations with external systems such as ERPs, CRMs, and part catalogs, and continuously improving our AI reasoning and retrieval capabilities. Aiventic is a long‑term SaaS product — it’s not a project with an endpoint, but an evolving platform built and refined with real user feedback from the field.

We operate in the field‑service and facility‑management domain, delivering a web‑based platform optimized for desktop and mobile browsers (PWA). The system consists of a React front‑end app, a. NET API layer, and integration modules that connect to various data sources. Our AI layer leverages Semantic Kernel, OpenAI APIs, and Azure Cognitive Search to reason over manuals, historical job data, and structured knowledge.

The tech stack includes. NET 8, C#, Entity Framework Core, SQL Server, Azure Functions, and Azure Service Bus on the backend; React 18, TypeScript, Vite, and TailwindCSS on the frontend; with infrastructure fully hosted in Azure, using Azure DevOps and GitHub Actions for CI/CD.

We’re a small, experienced team working closely together on architecture, features, and research. While the CTO and tech leads guide direction, everyone has real influence over technology choices and implementation. We care about clean code, clarity, and moving fast — building tools that truly help people get real work done.

Your responsibilities

• Lead the design and development of modern full‑stack applications using. NET 8, C#, and React.
• Integrate cutting‑edge AI features using Semantic Kernel and GenAI APIs.
• Model, optimise, and manage data in SQL.
• Build and maintain cloud‑native solutions in Azure (Functions, Service Bus, App Services, Blob Storage).
• Mentor a tight‑knit team (1–2 developers), take ownership of code reviews and technical growth.
• Shape the product’s technical direction — you’re not just a coder, you’re a driver.
• Collaborate across product, AI and dev teams to define, ship, and refine high‑impact features.
• Contribute to architecture, performance tuning, and automation in the DevOps pipeline.

Our requirements

• 5+ years of professional experience in. NET / C#.
• 3+ years of experience in React / TypeScript.
• Strong command of Azure cloud services and CI/CD pipelines.
• Solid experience with SQL and Entity Framework Core.
• A full‑stack mindset — you’re comfortable both backend and frontend.
• A self‑starter who brings ideas, drives initiatives, and owns outcomes.
• Excellent communication and collaboration skills.
• Bonus points: Experience with AI/LLM integrations (OpenAI, Semantic Kernel, etc.).

Division of working time

• 85% Programowanie
• 15% Calle

This is how we organize our work

• you focus on a single project at a time
• you develop the code "from scratch"
• you focus on product development
• agile
• scrum

This is how we work on a project

• Clean Code
• code review
• design patterns
• static code analysis
• architect / technical leader support
• Continuous Integration
• DevOps

Development opportunities we offer

• mentoring
• space for experimenting
• the company supports open source projects

What we offer

• Build a real‑world AI product used by field service professionals across North America.
• Work with a small, senior, fast‑moving team — no micromanagement, no corporate drag.
• Ship features that genuinely make technicians’ lives easier.
• 100% remote.
• Huge opportunity to grow into a lead role as the team scales.
• Bring your creativity, your voice, your initiative. Own the tech, the team, the product.

Benefits

• remote work opportunities
• flexible working time
• integration events

Recruitment stages

• Initial video call with CTO
• Brief take‑home assignment
• Technical discussion with Piotr about the assignment
• Final interview with CEO (in English)

⚙ Tech Stack

• NET 8 / C# / MediatR / EF Core
• React / TypeScript / Tailwind / Vite
• Azure (Azure SQL, Azure Functions, Service Bus, Blob Storage, App Insights)
• Semantic Kernel / OpenAI GPT API
• GitHub Actions / Docker / CI-CD

Interested?

Send us your GitHub or portfolio link and a short note about something you’ve built that you’re proud of.

About the Company

APPSTREAM STUDIO LLC

AppStream Studio — the innovation consultancy behind Aiventic. ai — is looking for a Senior Full‑Stack Engineer who doesn’t just code, but leads, innovates, takes ownership, and brings fresh thinking to the table. You’ll help build and scale Aiventic: an AI‑powered platform that empowers technicians to diagnose issues, identify parts, and finish repairs faster.

AppStream Studio is a Microsoft‑certified innovation consultancy and product studio. We help enterprises and PE‑backed companies design, build, and scale next‑generation software — blending deep .NET expertise with modern AI and product strategy.