Jobs → Engineering → Backend Engineer

About the Role We are looking for a Backend Engineer to join Koinworx in the Netherlands. This role requires 8+ years of experience and focuses on building scalable backend systems using C#/.NET. Key Responsibilities • Design and implement RESTful APIs and GraphQL services • Develop and maintain microservices architecture • Integrate with third-party APIs and handle service failures • Implement security best practices and graceful failure handling • Collaborate with product team on technical requirements • Lead code reviews and ensure code quality Requirements • Strong experience in C#, .NET 8 and ASP.NET Core MVC • Expertise in REST APIs, GraphQL, JSON and API versioning • Experience with Dependency Injection, Middleware, JWT, OAuth/OIDC, MediatR and FluentValidation • Hands-on experience with HttpClientFactory, Polly and third-party API integrations • Experience with unit and integration testing using xUnit, NSubstitute and FluentAssertions • Knowledge of AWS ECS Fargate, Lambda, SQS/SNS, DynamoDB and Redis • Experience with Terraform, GitLab CI/CD, AWS Secrets Manager and Datadog • Understanding of Server-Driven UI, Backend-for-Frontend and mobile application backend services • Experience with modular architecture, caching, performance optimization and production support • Strong knowledge of API contracts, backward compatibility, security and graceful failure handling • Backend development experience and hands-on C#/.NET experience • Experience owning backend services, architecture, releases and production support • Ability to work with large existing codebases and improve maintainability • Experience integrating multiple partner APIs and handling service failures • Strong collaboration, communication and technical decision-making skills