Full-Stack Developer (.NET + React, React Native)

Quick Facts

• Role: Full-Stack Developer (.NET + React, React Native) — Mid or Senior

• Contract: B2B (hourly billing)

• Work model: 100% remote from Poland

• Language requirement: fluent Polish required; English B2+

Description

You will help build an end-to-end digital platform for a large fitness club network, spanning a React Native mobile app, a React web back-office, and a .NET backend. The work includes feature development, REST API and service development, integrations with external systems (e.g., payment and notification), and maintaining code quality through tests, code reviews, and technical documentation. Deployments are handled with active team collaboration.

Responsibilities

• Design and implement new features across mobile (React Native), web (React), and server (.NET/C#)

• Create .NET-based services and REST APIs using .NET Core/.NET 8+ and SQL Server

• Integrate the platform with external systems such as payment gateways and notification systems

• Write unit and integration tests, run code reviews, and keep technical documentation

• Collaborate with the team on application deployment processes

Requirements

• Commercial experience: min. 3 years (Mid) / min. 5 years (Senior)

• Backend: strong C#, .NET Core/.NET 8+, ASP.NET Web API, Entity Framework Core, SQL Server

• Frontend & mobile: practical experience with React, React Native, TypeScript, JavaScript, HTML5, CSS3

• Knowledge of Clean Code, SOLID, and design patterns

• Daily practical usage of AI coding tools (e.g., GitHub Copilot, Claude Code, ChatGPT, OpenAI API)

• Fluent Polish (mandatory) and English at least B2 (spoken and written)

• Self-discipline, ability to organize remote work, and effective teamwork

• Senior only: practical microservices and cloud-native architecture experience; Azure services (App Services, Service Bus, Azure SQL, Azure DevOps); Docker

Benefits

• Fast start: start immediately (client may wait up to 2 weeks)

• Stability: B2B contract for at least 3 months with potential long-term extension

• 100% remote: no office/client visits required

• Recruitment: single-stage process (technical interview with developers + HR) with feedback in about a week