Senior .NET Backend Engineer

Celsus Engineering AB; Sweden; On-site; SEK 543,892 - 761,448; Full time

Job summary

Celsus Engineering AB in Sweden is seeking a skilled engineer to build a next-generation payment platform. You will design, optimize, and operate data-intensive systems while collaborating in a cross-functional team.

The ideal candidate has experience with .NET/C# and a strong understanding of microservices and data reliability. Knowledge of containerized environments and CI/CD pipelines is highly desirable.

Qualifications

• Proven ability in data-intensive systems with MS SQL Server.
• Deep understanding of database performance and reliability.
• Experience in .NET/C# and microservice architectures.

Responsibilities

• Design, optimize, and operate data-intensive systems.
• Build and operate backend services in a cross-functional team.
• Contribute to CI/CD pipelines for database changes.

Skills

Design and optimize data-intensive systems

Database performance and reliability

Building backend services using .NET/C#

Asynchronous messaging and event-driven systems

Containerized environments (Docker, Kubernetes)

CI/CD pipelines

Strong communication skills

Job description

Description

Build the next-generation payment platform on a modern and future-proof tech stack. Working in a cross-functional team

What we’re looking for

• Proven ability to design, optimize, and operate data-intensive systems, including schema design, performance tuning, and production troubleshooting in MS SQL Server–based environments.
• Deep understanding of database performance and reliability, including indexing strategies, query optimisation, and handling production issues.
• Experience building and operating backend services using .NET/C#, with a solid understanding of microservice architectures and distributed systems.
• Experience designing and working with asynchronous messaging and event-driven systems, using Kafka, IBM MQ, or similar technologies.
• Experience running services in containerised and orchestrated environments (Docker, Kubernetes/OpenShift), with awareness of scaling, resilience, and failure modes.
• Experience contributing to or owning CI/CD pipelines for database changes and deployment automation, with a focus on safe, repeatable releases.
• A collaborative engineering mindset, with a willingness to share knowledge, learn continuously, and improve how the team builds and runs software.
• Meritorious with experience from financial services, payments, or other regulated environments.
• Strong communication skills, with fluency in English; Swedish is a plus.