Developer .NET

CONTRACT DURATION: ASAP - 04/11/2027+ Possible of Extension

Job description – Backend Developer (C# / .NET)

About the position

• As a Backend Developer, you will be responsible for developing, extending and maintaining high-performance, secure and scalable backend functionalities within our C# / ASP.NET Core architecture.
• You work within a modular architecture in which generic functionalities are housed in shared libraries that are reused across different applications. In addition, you develop application- and domain-specific functionalities.
• You translate functional needs into clear data models, services and APIs and ensure that data is made available on the front-end in a consistent and actionable way. You will work closely with front-end developers on API contracts and data models.

Primary responsibilities

• Developing and maintaining backend functionalities in C# and ASP.NET Core.
• Developing new features and modules within both the shared libraries and the application-specific layer. Designing, developing and maintaining REST APIs.
• Setting up and maintaining data models and data processing via Entity Framework Core and MSSQL.
• Integrate and consume internal and external APIs.
• Converting and structuring external data into usable data models for the application.
• Align with front-end developers on API contracts, data models, validations, and error handling.
• Developing robust backend functionalities that correctly deal with erroneous, incomplete or unexpected input.
• Writing and maintaining unit and integration tests.
• Testing, debugging, and resolving technical issues.
• Monitoring and optimizing performance, stability, security and code quality.
• Apply principles for secure software development, including input validation and relevant OWASP guidelines.
• Documenting code, APIs and key technical choices.

Secondary responsibilities

• Contribute to the further development and improvement of the modular back-end architecture.
• Contribute to the further standardization and reusability of common components.
• Performing and participating in code reviews.
• Thinking along about architectural and technical choices.
• Integrating Elasticsearch for search functionalities.
• Use Elastic APM for tracing and monitoring.
• Implement and maintain background processes and planned tasks, for example via Hangfire.
• Collaborate within the existing GitLab CI/CD environment and deployment to Kubernetes.

Your profile

• Proven experience in the development of .NET-based applications.
• Proven training with certification or equivalent through experience in programming languages and environments such as C#, .NET and ASP.NET Core.
• Demonstrable experience to carry out programming assignments smoothly: analyzing, coding, testing and debugging, independently if necessary.
• Demonstrable knowledge of and experience with Agile development methodologies.
• Language requirement: Dutch at European CEFRlevel C2.
• Strong knowledge of C# and ASP.NET Core.
• Experience with Entity Framework Core or a similar ORM.
• Experience with relational databases and SQL, preferably MSSQL.
• Experience in developing and consuming REST APIs and processing JSON.
• Understanding modular software architecture and the separation between shared and domain-specific functionalities.
• Experience with Git and version control.
• Experience with automated testing, including unit and integration testing.
• Attention to software security, input validation, error handling and OWASP principles.
• Able to independently analyze technical problems and arrive at a maintainable solution.
• Pros: Experience with Elastic/Elasticsearch, Elastic APM, Hangfire, GitLab CI/CD, Docker/Kubernetes and/or Vue.js.

Skills

• Proven experience working with Git.
• Proven experience in developing .NET-based applications.
• Demonstrated experience with Entity Framework (or a similar ORM) and relational databases.
• Proven experience with automated testing (unit and integration testing).
• Proven experience in setting up and consuming REST APIs.
• Demonstrable knowledge and attention to security and input validation (OWASP awareness).
• Demonstrable knowledge of C# and ASP.NET Core.
• Demonstrated knowledge of modular architecture: separation between shared and domain-specific code.
• Demonstrable training with certification or equivalent through experience in programming languages and environments such as .Net (C#), ASP.NET, .
• Language requirement: Dutch at European CEFR - level C2.
• Be able to perform demonstrable expe