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.

Tagged as: IT & data communications