Senior Full-Stack Web Developer (C#, Rest API, Docker)

Backend REST API Developer C# ASP.NET Shape the Future of IT with Advaun Advaun Oy builds software that helps businesses run better. We develop web applications, AI systems, healthcare and industrial software, and our own AI-powered ERP/MES platform for manufacturers. We are looking for a Full-Stack / Backend Developer with strong C# and ASP.NET experience to join our team in Helsinki/Espoo. The role focuses on building a REST API with C# and ASP.NET to interface with a legacy application database and support integrations with third-party products. Responsibilities Design, build, and maintain REST APIs using C# and ASP.NET Work with legacy application databases and third-party integrations Use Entity Framework Core with Microsoft SQL Server Implement authentication and authorization with Keycloak and OpenFGA Design and document APIs with OpenAPI / Swagger Write clean, testable, production-quality code Build automated tests using MSTest, Reqnroll, and integration testing tools Work with Docker-based development and deployment environments

✅Requirements

3+ years of software development experience Strong experience with C# and ASP.NET / ASP.NET Core Solid understanding of REST APIs, OpenAPI, and software testing principles Experience with Entity Framework Core and Microsoft SQL Server Experience with Docker Independent and solution-oriented mindset Fluent English Located in the Helsinki greater region or able to commute daily Full-time on-site work in Helsinki/Espoo, minimum 4 days per week Please note: we are not able to offer relocation packages or visa support Tech Stack Core: C#, ASP.NET / ASP.NET Core Data: Entity Framework Core, Microsoft SQL Server, PostgreSQL Auth: Keycloak, OpenID Connect, OpenFGA API: REST APIs, OpenAPI / Swagger Testing: MSTest, Reqnroll, Microsoft.AspNetCore.Mvc.Testing DevOps: Docker, Kubernetes, Azure DevOps, GitHub Actions, Azure Container Registry Nice to Have Knowledge of HL7 FHIR Experience in healthcare software development Experience with legacy systems or database integration What We Offer A key role in a growing startup Work on real healthcare, industrial, AI, and ERP/MES software Modern technical environment Supportive team culture Office in Helsinki/Espoo Weekly yoga, Monday breakfast, 24/7 gym, and team events Apply Send your CV and salary expectations here: https://forms.gle/Svjd4TwrRKDuSYAA8 Recommended: GitHub or coding sample, LinkedIn profile, or personal website We review applications on a rolling basis and may fill the position before the deadline.

Advaun Oy builds software that helps businesses run better. We develop web applications, AI systems, healthcare and industrial software, and our own AI-powered ERP/MES platform for manufacturers. We are looking for a Full-Stack / Backend Developer with strong C# and ASP.NET experience to join our team in Helsinki/Espoo. The role focuses on building a REST API with C# and ASP.NET to interface with a legacy application database and support integrations with third-party products.