*Freelance Senior .NET / C# Backend Engineer | B2C Digital Platform | Rotterdam / Hybrid*

For a key player in the Dutch energy transition, we are looking for a Senior Freelance .NET / C# Backend Engineer who enjoys working in complex, high-traffic digital environments.

You will help build and evolve a modern B2C platform used by millions of customers, where scalability, reliability, and clean architecture are essential. Within a cross-functional product team you will design and develop scalable backend services that power digital customer journeys, identity management, and data-driven customer insights.

This role combines hands-on engineering with architectural ownership in a modern cloud-native environment.

What you’ll do

As a Senior Backend Engineer you will play a key role in building and improving backend systems that support a large-scale B2C digital ecosystem.

Your responsibilities include:

• Designing and building scalable backend services in .NET / C#
• Developing microservices and event-driven integrations
• Building services around customer onboarding, identity management, and customer journeys
• Integrating systems through APIs and event streaming platforms
• Ensuring performance, security, reliability and high availability
• Driving technical decisions and architectural improvements
• Supporting CI/CD pipelines and cloud-native best practices
• Mentoring engineers and contributing to engineering standards within the team
• Improving observability, monitoring and operational excellence

You will work closely with other engineers, QA specialists, and product managers in a cross-functional product team focused on delivering high-quality digital solutions.

Tech stack

• .NET / C#
• Microsoft Azure
• Kubernetes / containerization
• Kafka / Event Hubs / messaging
• SQL
• Azure DevOps
• Terraform / Infrastructure as Code
• gRPC / API integrations
• Event-driven architectures

Requirements

• 5+ years of experience in backend development with .NET / C#
• Strong experience with cloud-native architecture (Azure preferred)
• Experience with microservices, containerization and CI/CD pipelines
• Proven experience designing event-driven architectures
• Experience building scalable and secure services
• Experience with messaging platforms (Kafka, Event Hub, RabbitMQ or similar)
• Strong understanding of observability and monitoring in cloud environments
• Based in the Netherlands
• Fluent in English
• Collaborative mindset and comfortable working in multidisciplinary product teams

Nice to have

• Experience with B2C platforms with high user volumes
• Experience with identity & access management platforms (e.g. Okta)
• Experience working in regulated or infrastructure-heavy environments
• Experience with SLIs / SLOs and reliability engineering

Practical details

Location: Rotterdam (2 days onsite, remainder remote)

Start: March / April

Duration: Minimum 6 months (expected 12+ months)

Contract: Freelance / ZZP

If you're interested, feel free to reach out directly or send a message for more details.