Senior .NET Developer

Quick Facts

• B2B Contract (12 months, possible extensions)
• Warsaw, Poland (2–3 days/week in the office, the rest remote)

Description

We are looking for an experienced Senior .NET Developer to take ownership of a business-critical enterprise integration platform 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 opportunity to contribute to modernising an established .NET Framework solution.

Responsibilities

• Maintain and extend an established C# / .NET Framework 4.x Windows Service
• Support multi-threaded, timer-driven import and export processing
• Investigate and resolve production issues across application and data layers
• Develop and optimise SQL Server / T-SQL solutions
• Maintain stored procedures and Dapper-based repositories
• Analyse and resolve locking, deadlock, and performance issues
• Maintain mappings between enterprise canonical data models
• Work with shipment, status event, milestone, and customs declaration data
• Maintain WCF / SOAP integrations, including service references, bindings and endpoints
• Work with XML serialisation, XSD schemas, and XSLT mappings
• Provide 2nd and 3rd level production support
• Reprocess and correct data when required
• Work closely with business, operations, integration, and master data teams
• Contribute to unit and integration testing, code reviews, and technical documentation
• Support the platform modernisation roadmap
• Contribute to potential migration toward modern .NET, standard Dependency Injection, and REST-based integrations

Requirements

• 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, and 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

Benefits

• Opportunity to take ownership of a business-critical integration platform
• Production support responsibilities with data reprocessing and correction
• Chance to contribute to the modernization roadmap, including possible migration toward modern .NET and REST-based integrations
• Hybrid work model: 2–3 days/week in the Warsaw office, rest remote