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Offer summary
(Summary generated by AI based on the full job description)
The project involves modernization and development of laboratory and diagnostics systems for an international organization. Technologies used include ASP.NET Core, C#, React, and WPF. Responsibilities cover designing and maintaining fullstack applications, refactoring monolithic systems, enhancing UI components, and collaborating on architecture and code reviews. Knowledge of monolithic architectures and ensuring high-quality, performant code is required.
Senior Fullstack .NET Developer (f/m/x)
Company: Sii Sp. z o.o.
from: 29 May 2026
to: 28 June 2026
salary not specifiedB2B contract (full-time)
salary not specifiedcontract of employment
Offer parameters
level:senior
working mode:hybrid • full office
Wrocław, Fabryczna
Requirements
Expected technologies
C#
ASP.NET Core
React.js
JavaScript
WPF
Optional technologies
REST
Entity Framework
Microsoft Azure
Git
Our requirements
- At least 6 years of experience as a .NET/Fullstack Developer
- Strong hands-on experience with C#, ASP.NET Core, and React/JavaScript
- Knowledge of monolithic architectures and refactoring approaches
- Experience with WPF or willingness to maintain existing desktop components
- Very good English (B2+) for daily communication in an international environment
- Fluent Polish required
- Residing in Poland required
Your responsibilities
- Design, develop, and maintain fullstack applications using ASP.NET Core, C#, and React
- Modernize and refactor existing monolithic systems, ensuring performance and scalability
- Implement and enhance UI components, including working with WPF where necessary
- Collaborate with cross‑functional teams on architecture, code reviews, and technical direction
- Troubleshoot, optimize, and ensure high-quality, testable, and maintainable code
About the project
We are looking for a highly experienced Fullstack .NET Developer with strong React skills to join a long‑term project delivered by Sii for an international organization recognized for its advanced laboratory and diagnostics technologies. You will work on the development and modernization of complex systems, including legacy monolithic applications and WPF components, while contributing to new features built on ASP.NET Core and modern JavaScript frameworks.
The role is hybrid, with 2–3 days per week in our Wrocław office.
If you're ready for your next big challenge — apply now!
What we offer
- Great Place to Work since 2015 - it’s thanks to feedback from our workers that we get this special title and constantly implement new ideas
- Employment stability - revenue of PLN 2.1BN, no debts, since 2006 on the market
- We share the profit with Workers - over PLN 76M has already been allocated for this aim since 2022
- Attractive benefits package - private healthcare, benefits cafeteria platform, car discounts and more
- Comfortable workplace – class A offices or remote work
- Dozens of fascinating projects for prestigious brands from all over the world – you can change them thanks to Job Changer application
- PLN 1 000 000 per year for your ideas - with this amount, we support the passions and voluntary actions of our workers
- Investment in your growth – meetups, webinars, training platform and technology blog – you choose
- Fantastic atmosphere created by all Sii Power People
Recruitment stages
- 1.Send your CV
- 2.Talk to us about your expectations
- 3.Learn more about our projects and choose the best
- 4.Start your adventure with Sii!
Sii Sp. z o.o.
Sii is the leading technology consulting, digital transformation, engineering, and business services vendor in Poland. We already employ more than 7 300 professionals and implement projects in a variety of industries for clients from many countries around the world. The Great Place to Work title, won 10 times in a row, proves that at Sii, we create a friendly work environment.
Sii ensures that all employment-related decisions are made solely on the basis of qualifications and competencies. We are committed to equal treatment of all individuals, regardless of any protected characteristics, and promoting a diverse and inclusive work environment.
This is how we work
Senior Fullstack .NET Developer (f/m/x)
I apply to:
Sii Sp. z o.o.
Wrocław, Fabryczna
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