Senior .NET Developer

About the project

Start: December 1, 2026

📍Location: hybrid work in Warsaw (3 days per week working from Warsaw office)

This is how we organize our work

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

Our requirements

• 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

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

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!