Senior Software Developer C#

Job Duties

Landmark, a Halliburton company, builds the software and data platforms that help the global energy industry make better decisions. Our products span subsurface interpretation, well construction planning, reservoir simulation, and digital operations — tools used daily by engineers and scientists at the world’s largest energy companies. We are investing significantly in our engineering capability in Oslo, and these roles are part of building a permanent, locally-owned engineering organization to take long-term ownership of the platform.

We are hiring experienced C# developers to build and evolve the .NET services at the core of the platform. These are backend roles on services that handle demanding, domain-rich workloads in the energy space — services that need both ongoing feature development and the careful maintenance that keeps a production platform reliable. Parts of the codebase are written in F#, so comfort with — or a willingness to pick up — a functional style alongside C# is a welcome plus. You will work in a modern microservices environment with REST and message-based communication, in a team that takes engineering quality seriously and treats AI-assisted development as a normal, everyday way of working. You will collaborate closely with other backend and full-stack engineers, and your work will sit directly behind tools that engineers and scientists at major operators rely on.

Backend Service Development

• Design, build, and maintain .NET backend services in C#, using ASP.NET Core and an ORM such as Entity Framework, to deliver and evolve platform capabilities.
• Work across parts of the codebase written in F#, contributing to or extending functional code where the platform uses it.
• Own features end to end — from design through implementation, testing, and production support — with a high degree of personal ownership.

Architecture and Integration

• Build within a microservices architecture, designing clean REST APIs and message-based integrations between services.
• Make pragmatic design decisions about service boundaries, data access, and inter-service communication, and contribute to the platform’s evolving technical standards.
• Integrate with the platform’s data stores and streaming infrastructure, working alongside the data and DevOps teams as needed.

Quality and AI-Assisted Engineering

• Hold a high bar for code quality — automated testing, code review, and maintainable design — so the platform stays fast and safe to change.
• Use AI-assisted coding tools (Claude Code, Copilot, and similar) as a normal part of your daily workflow to work faster without lowering the quality bar.
• Contribute to a strong, collaborative engineering culture: sharing knowledge, reviewing peers’ work constructively, and helping raise the team’s overall standard

Qualifications & Experience

• Master’s degree in Computer Science, Software Engineering, or a closely related STEM discipline.
• Strong C# with solid production experience building backend services.
• .NET backend development experience, including ASP.NET Core and Entity Framework or a similar ORM.
• Comfortable with microservices architecture, REST API design, and message-based communication between services.
• Proficient with AI-assisted coding tools (Claude Code, Copilot, or similar) in daily work.

Preferred

• F# experience, or a genuine willingness to learn and work in F# (parts of the codebase use it).
• Experience with PostgreSQL, Kafka, Kubernetes, and Azure.
• Exposure to the oil & gas or wider energy domain.
• Experience working in a monorepo with code review, and with continuous integration and incremental delivery.
• We welcome candidates from all backgrounds and encourage you to apply even if your experience does not match every item in the preferred list.

Why Landark

These roles are part of a deliberate investment in building a permanent engineering organization in Oslo, with real ownership of a platform used across the global energy industry. We build small, high-ownership teams and invest in the quality of every person on them. Engineers here co-author the product strategy alongside product management and domain science: the art of the possible is an engineering contribution, not a function that sits upstream. You will work in a business where software is the product, solving technically demanding problems in a domain where your improvements have visible, measurable impact. We offer competitive compensation including bonus and long-term incentive programs, and the scope to build something that lasts.