Senior .NET Developer w Warszawa, Polska

Expected, .NET, C#, SoapUI, SQL

About the project, Start: December 1, 2026, , Location: hybrid work in Warsaw (3 days per week working from Warsaw office)

This is how we work, at the client's site

Your responsibilities, Maintain and extend the Windows Service (C#, .NET Framework), including its multi-threaded, timer-driven import and export processing., Develop and optimise SQL Server data access: stored procedures, Dapper-based repositories, and handling of deadlocks, locking and performance issues., Maintain mappings between canonical data models for shipments, status events, milestones and customs declarations, using AutoMapper and custom merge logic., Maintain and update WCF/SOAP integrations, such as the DAAC master data and configuration services and the export service agents., Provide 2nd/3rd-level production support: analyse data issues, reprocess or correct records, and resolve incidents together with operations and business teams., Document the current solution and contribute to its modernisation roadmap, e.g. migrating to modern .NET, standard dependency injection and REST-based integrations., Drive quality through unit and integration testing

You are an experienced, quality-focused developer who is comfortable working with established enterprise systems, enjoys solving complex data problems, and communicates clearly with both technical and business stakeholders., 5+ years of proven experience as a .NET Developer, Software Engineer, or in a similar role., Strong proficiency in C# and .NET Framework 4.x, including Windows Services, multithreading with the Task Parallel Library., Solid experience with Microsoft SQL Server and T-SQL: backup, stored procedures, query tuning, transactions, isolation levels and deadlock analysis., Hands-on experience with WCF/SOAP services, including generating and maintaining service references and configuring bindings and endpoints., Experience with XML serialization and XSD schemas, XLST maps, and with object mapping libraries such as AutoMapper, Familiarity with dependency injection (e.g. Unity)

What we offer, We offer a full-time employment contract, • Location – Warsaw; work model – hybrid, • Stable and long-term cooperation, • Well-defined career path at the European leader in engineering & IT consulting, • Opportunity to relocate and work in different ALTEN Polska branches, • After completion of the project, opportunity to engage in a subsequent one within the company, • Introduction and cooperation with dedicated Competences Manager, , We also offer cooperation based on a B2B or Contract of mandate (UZ)., , We also guarantee:, • Access to professional certifications with our technology partners (e.g. Google, ISTQB), • Access to relevant industry events, • Access to the Knowledge Sharing Program, • Access to Referral program

Benefits, life insurance, retirement pension plan, baby layette, employee referral program, Medicover medical care , Medicover dental care , Medicover Benefits platform , Medicover Sport card

ALTEN Polska, WHO ARE WE?, , WE ARE A WORLD LEADER IN ENGINEERING AND IT SERVICES., , At ALTEN, we see our specialists as architects – today’s designers of tomorrow’s world., As a leader in Engineering and IT Services, we support companies in their technological and sustainable transformation., , OVER 57,400 EMPLOYEES IN 30+ COUNTRIES, TO SUPPORT MORE THAN 6,500 CLIENTS WORLDWIDE., , We operate in all sectors: Aeronautics, Space, Defence, Security & Naval, Automotive, Rail & Mobility, Energy & Environment, Life Sciences & Health, Industrial Equipment & Electronics, Telecoms, Banking, Finance & Insurance, Retail, Services & Medias, Public Services & Government., , We carry out complex and highly technical projects throughout the value chain of the most prestigious companies worldwide., , Our motto: Building Tomorrow’s World Today!