Senior Backend .NET Developer

Twoday Denmark; København; On-site; DKK 900,000 - 1,150,000; Full time

Job summary

Twoday is seeking a Senior Backend .NET Developer for a Copenhagen delivery that will play a key part in building and operating critical healthcare software. You will design and implement robust backend services, APIs and data models, collaborating with Solution Architects, testers, DevOps and product stakeholders.

The role emphasizes secure, scalable systems, production readiness and long‑term, cross‑company teamwork.

Qualifications

• Experienced backend engineer with strong C# and .NET foundations.
• Experience designing and implementing backend services and APIs in complex environments.
• Proven ability to work across teams in a collaborative development culture.
• Familiarity with healthcare or regulated public-sector IT is a plus.

Responsibilities

• Design, develop and maintain backend services and server‑side components.
• Develop APIs and integrations across a complex application landscape.
• Contribute to data modelling and architectural decisions.
• Work with microservices, distributed systems and event‑driven architectures.
• Design for resilience, scalability, and operational stability.
• Implement logging, monitoring and observability in production.
• Build and maintain automated pipelines for build, test and deployment.
• Contribute to containerised deployment and modern infrastructure practices.
• Follow secure coding practices and ensure security throughout the lifecycle.
• Write automated tests and uphold high code quality and documentation standards.
• Diagnose and resolve issues across release and production environments.
• Translate requirements into technically sound solutions and share knowledge across teams.

Skills

C#/.NET

ASP.NET Core

REST APIs

Microservices

Kafka

SQL

DDD

Docker

CI/CD

Azure DevOps

Git

Testing

Observability

Security

Resilience

Agile

Tools

Docker

Kafka

Job description

Permanent position at Twoday | Copenhagen

Senior Backend .NET Developer

Do you want to build and evolve business-critical digital solutions that support Denmark’s healthcare sector?

Twoday is looking for experienced Backend .NET Developers to join a major, long-term digital health delivery in Copenhagen. You will work with complex systems where reliability, security, maintainability and technical quality are essential – and where the solutions you help build and operate have a direct impact on critical public services.

This is a permanent position with Twoday, where this delivery would, if we win the tender, become your first assignment as a consultant with us.

The role

The customer is introducing a new delivery model in which several suppliers will collaborate closely on the development, maintenance and operation of a portfolio of business-critical healthcare applications.

Rather than operating as separate supplier organisations, developers from different companies will work together in shared teams. This makes technical expertise essential, but it also requires engineers who collaborate well, share knowledge and take responsibility for the overall delivery – not just their own code.

As a Senior Backend .NET Developer, you will work hands‑on throughout the software delivery lifecycle: from analysis and refinement through design and development to testing, deployment, maintenance and troubleshooting in production.

You will be expected to contribute to building robust solutions and to take technical ownership in close collaboration with other developers, Solution Architects, testers, DevOps specialists and product stakeholders.

Your responsibilities will include:

• Designing, developing and maintaining backend services and server‑side components

• Developing APIs and integrations across a complex application landscape

• Contributing to application design, data modelling and technical decision‑making

• Working with microservices, distributed systems and event‑driven architectures

• Designing for resilience, scalability, high availability and operational stability

• Working with messaging technologies and asynchronous communication

• Building and maintaining automated build, test and deployment pipelines

• Contributing to containerised deployment and modern infrastructure practices

• Implementing appropriate logging, monitoring and observability

• Applying secure coding practices and considering security and privacy throughout the development lifecycle

• Writing automated tests and contributing to high standards for code quality and documentation

• Diagnosing and resolving issues across release and production environments

• Contributing to backlog refinement and translating requirements into technically sound solutions

• Sharing knowledge and collaborating across teams and suppliers

The formal role includes both development and operation of server‑side components as well as version control and automated pipelines.

What we are looking for

You are an experienced, hands‑on backend engineer with a strong foundation in C# and .NET and a track record of developing complex, business‑critical software.

You are comfortable looking beyond an individual feature or service and understand how architecture, integration, data, security, deployment and operations come together in a production environment.

We are particularly interested in experience with several of the following:

• C# and modern .NET / .NET Core

• ASP.NET Core and backend service development

• REST APIs and systems integration

• Microservices and distributed systems

• Messaging and event‑driven architectures, such as Kafka or comparable technologies

• SQL, data modelling and transactional systems

• Domain‑driven design and modern software architecture principles

• Docker, containers and modern deployment practices

• CI/CD and automated delivery pipelines

• Azure DevOps or comparable engineering platforms

• Git and collaborative development workflows

• Automated testing and quality engineering

• Observability, monitoring and production troubleshooting

• Authentication, authorisation and secure software development

• Resilience patterns and highly available systems

• Agile software development

Experience from healthcare, Danish public‑sector IT or other complex and regulated environments is a strong advantage.

Healthcare knowledge is not a prerequisite for every position on the team, but relevant experience from the healthcare domain will be particularly valuable.

Who you are

You are still close to the technology and enjoy solving difficult engineering problems.

You take ownership of your work from understanding the problem to seeing the solution perform reliably in production. At the same time, you recognise that seniority is not only about technical depth. You contribute constructively to technical discussions, challenge solutions when needed, support colleagues and help the team make sound engineering decisions.

The delivery will involve close collaboration across organisational boundaries, so you should be comfortable working transparently with colleagues from different companies and contributing to a shared engineering culture.

You must be fluent in spoken and written Danish and English.

The role is based in Copenhagen and requires a significant degree of onsite work at the customer.

Join Twoday

At Twoday, you will join a strong professional technology environment with colleagues working across software engineering, architecture, cloud, data and digital transformation.

This is a permanent position with Twoday, where this delivery would, if we win the tender, become your first assignment as a consultant with us. Your employment is with Twoday and is not limited to this particular customer or project.

For the right developer, this is an opportunity to combine deep backend engineering with a long‑term assignment in an important and technically complex area of Danish digital infrastructure.

We look forward to hearing from you.

Working at Twoday

Twoday is a leading technology consulting company specializing in applied AI and advanced engineering. With around 2,300 experts in AI, data, digital engineering, and cloud engineering, we cut through complexity, remove uncertainty, and prove the value of technology.

Our purpose is to create a better tomorrow through AI and technology. We strengthen private and public organizations across energy and utilities, financial services and insurance, industrials and manufacturing, health and life sciences, and government.

However, our greatest strength isn't the technology we work with. It’s the people behind it. Every day, they bring together expertise, curiosity, and determination to help our customers solve complex challenges and create lasting value.

Diversity and inclusion

We are committed to building an inclusive and diverse workplace where everyone is treated with respect and has equal opportunities. Our recruitment decisions are based on competencies, experience, and individual merit.

Don’t meet all the requirements? Many candidates hesitate to apply unless they meet every qualification. We are looking for people who are engaged, meet most of the criteria, and are motivated to grow in the role. If this role interests you and you believe you could be a good fit, we encourage you to apply.