Senior Backend Engineer (C#/.NET) - Remote

About the role

A client of Castille Resources is looking for a Senior Backend Engineer to join its engineering team on a remote, project-based B2B assignment. The engineer contributes to scalable, secure and reliable backend systems supporting payment services and integrations across multiple markets, working with cross-functional teams to build high-performance applications, APIs and microservices. The engagement lasts 6 months, with possible extension, and requires a CET timezone.

Key responsibilities

• Design, develop and maintain server-side applications using C# and the .NET framework.
• Build secure RESTful APIs and microservices for client apps, payment services and integrations.
• Design and maintain distributed systems made of multiple domain-oriented services.
• Test, debug and review code, and optimise performance through caching and database tuning.
• Write and optimise SQL queries and work with PostgreSQL and SQL Server, and NoSQL databases.
• Help deploy and maintain applications on cloud platforms, with containerisation and orchestration.
• Improve development processes and architecture with engineering teams.

Required profile

• At least 5 years of experience in backend software engineering or a similar role.
• Strong hands-on experience with C# and the .NET framework.
• Experience with RESTful APIs, microservices, distributed systems and relational databases (PostgreSQL, SQL Server).
• Familiarity with NoSQL databases, cloud platforms (Azure or AWS), Git, Docker and Kubernetes.
• Good English, able to work independently with international teams.

Nice to have

• Degree in Computer Science or a related field.
• Kafka, RabbitMQ, Redis, gRPC, Consul, etcd, Orleans.
• Payment systems experience.

The selection process includes a proposal submission, a 30-minute alignment call, vetting, a client interview and a technical assessment if required. Repeat engagements are possible based on performance.