Senior .NET Developer

• B2B Contract, 12 months + possible extensions
• Location: Warsaw, Poland
• Work model: 2-3 days/week in the office, the rest remotely

We are looking for an experienced Senior .NET Developer to take ownership of a business-critical enterprise integration platform responsible for consolidating shipment, status event and customs declaration data from multiple transport management systems. The role combines backend development, batch processing, SQL Server optimisation, enterprise integrations and production support, with an additional opportunity to contribute to the future modernisation of an established .NET Framework solution.

Your responsibilities

• Maintaining and extending an established C# / .NET Framework 4.x Windows Service.
• Supporting multi-threaded, timer-driven import and export processing.
• Investigating and resolving production issues across application and data layers.
• Developing and optimising SQL Server / T-SQL solutions.
• Maintaining stored procedures and Dapper-based repositories.
• Analysing and resolving locking, deadlock and performance issues.
• Maintaining mappings between enterprise canonical data models.
• Working with shipment, status event, milestone and customs declaration data.
• Maintaining WCF / SOAP integrations, service references, bindings and endpoints.
• Working with XML serialisation, XSD schemas and XSLT mappings.
• Providing 2nd and 3rd level production support.
• Reprocessing and correcting data when required.
• Working closely with business, operations, integration and master data teams.
• Contributing to unit and integration testing, code reviews and technical documentation.
• Supporting the modernisation roadmap of the platform.
• Contributing to potential migration towards modern .NET, standard Dependency Injection and REST-based integrations.

Must-have experience

• 5+ years of professional experience as a .NET Developer / Software Engineer.
• Strong hands-on experience with C# and .NET Framework 4.x.
• Experience developing and maintaining Windows Services.
• Strong understanding of multithreading and the Task Parallel Library.
• Very good knowledge of Microsoft SQL Server and T-SQL.
• Experience with:
• stored procedures,
• query tuning,
• transactions,
• isolation levels,
• locking,
• deadlock analysis.
• Hands-on experience with WCF and SOAP services.
• Experience configuring service references, bindings and endpoints.
• Good knowledge of XML, XSD and XSLT.
• Experience with object mapping tools such as AutoMapper.
• Familiarity with lightweight ORMs such as Dapper.
• Experience with Dependency Injection / IoC frameworks.
• Experience with unit testing and mocking frameworks.
• Git experience.
• Strong analytical and troubleshooting skills.
• Very good English communication skills.

Nice to have

• Experience with freight forwarding, transport or logistics systems.
• Experience working with shipment, milestone or customs-related data.
• Experience modernising legacy .NET Framework applications
• Knowledge of Worker Services.
• Experience with Microsoft Azure services such as Azure Functions or App Services.
• Docker and Kubernetes experience.
• Agile / Scrum experience.

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