Senior .NET Framework Developer

Your tasks

We are looking for a Senior .NET Developer to join a business-critical integration project within the logistics industry.

The role combines maintaining and stabilising the existing solution with helping the organisation modernise its integration architecture.

This is not a maintenance-only position. You will have the opportunity to analyse the current platform at an architectural level, influence its future direction, and support the transition from .NET Framework and WCF-based integrations to modern .NET and REST APIs.

• Maintain, stabilise, and extend a business-critical application built with C# and .NET Framework
• Develop and optimise a multithreaded, timer-driven Windows Service responsible for batch import and export processes
• Analyse the existing solution, its architecture, dependencies, and data flows
• Support the modernisation and migration of the platform towards modern .NET and API-based integrations
• Maintain and gradually replace legacy WCF/SOAP services with REST APIs
• Develop and optimise Microsoft SQL Server data access, including stored procedures and Dapper-based repositories
• Troubleshoot SQL performance issues, transactions, locking, and deadlocks
• Maintain mappings between canonical data models for shipments, milestones, status events, and customs declarations
• Investigate production incidents, resolve data consistency issues, and reprocess or correct records when required
• Cooperate with business, integration, master data, and operations teams
• Support regular environment and platform updates
• Create and maintain technical and architectural documentation
• Contribute to unit and integration testing, code reviews, and continuous improvement of development standards
• Bring a system-level perspective to discussions about the current and target architecture

Requirements

• At least 6 years of commercial experience in .NET development or a similar software engineering role
• Strong hands-on experience with C# and .NET Framework 4.x
• Experience developing and maintaining Windows Services
• Practical knowledge of multithreading and the Task Parallel Library
• Strong experience with Microsoft SQL Server and T-SQL
• Hands-on experience with WCF/SOAP services
• Good understanding of REST APIs and modern integration approaches
• Experience with XML, XSD schemas, XML serialization, and XSLT mappings
• Knowledge of object mapping tools such as AutoMapper
• Experience with lightweight ORMs, preferably Dapper
• Familiarity with dependency injection
• Experience with unit testing frameworks such as MSTest and mocking libraries such as Moq
• Practical knowledge of Git
• Architectural mindset and the ability to understand dependencies between applications, services, and integrations
• Willingness to work with an existing legacy codebase while actively supporting its modernisation
• Fluent English, minimum C1 level
• Polish language proficiency

Nice to have

• Experience migrating applications from .NET Framework to modern .NET, including .NET 8+
• Knowledge of freight forwarding or logistics processes, including shipments, transport stages, and status events
• Experience with Microsoft Azure, particularly Azure Functions or App Services
• Familiarity with Docker and Kubernetes
• Understanding of enterprise integration or ESB environments
• Experience working in Agile or Scrum teams

Must have: .NET, SQL, REST, WCF, SQL Server, Git, Web API, MS SQL

Nice to have: Azure, Docker

What we offer

• Dedicated Agent support – your go-to person for project continuity, client communication, day-to-day administration, and long-term professional development
• Access to Darize Learning & Development – our internal development platform featuring webinars, industry reports and articles, access to learning platforms such as DataCamp and Coursera, and regular invitations to technical, business, and lifestyle events
• Community and networking events – from Kick-Off trips, Christmas celebrations, and Summer Sport Games to family picnics and cultural events for you and your loved ones
• Consultant Development Program – personalized professional development support based on current industry trends and market needs, delivered by experienced mentors and development advisors
• Comprehensive benefits package – including private healthcare, life insurance, a sports card for you and your family members, as well as access to employee discounts in Poland and abroad
• A community of experienced IT experts – exchange knowledge and collaborate with technology professionals who bring years of hands-on experience delivering complex technology projects (the average professional experience of our consultants in Poland exceeds 10 years)

Other

*Work Mode: hybrid from Warsaw office (3 days/week) *Start of the project: ASAP Duration of the project: till the end of 2027 (with possibility of extension)