Senior.NetFullstackEngineer

N-iX is a global software development company, empowering businesses worldwide with next-generation tech solutions. Since 2002, we have grown into a team of 2,400+ experts with offices in Kraków, Warsaw, and Wroclaw, and an active Polish community. We deliver high-impact projects for Fortune 500 clients and industry leaders, offering flexible work formats (remote, office, or hybrid) and lots of growth opportunities. Join us to create technology that drives real change for businesses and people across the world. N-iX is looking for a Senior .NET Fullstack Engineer to join the team working on the customer's product. You will join a functional team focused on building advanced tools, dashboards, and UIs for both external clients and internal users. The team's recent achievements include developing a new Client Dashboard and an Analyst Dashboard that enables the Operations team to efficiently track tasks and monitor their SLAs. Responsibilities: Design and develop scalable backend services using .NET. Apply Clean Architecture and DDD (Domain-Driven Design) principles. Build REST APIs and model domain logic. Optimize SQL/EF Core data access, SQL queries, and stored procedures. Ensure high code quality through testing and reviews. Identify and address performance bottlenecks in APIs and database queries. Contribute to system design and performance improvements. Requirements: 7+ years of experience with .NET and strong knowledge of C# fundamentals. 3+ years of experience with React, TypeScript, or Angular. Must-Have Tech Stack: C#, .NET 8/10, ASP.NET, MSSQL, Web API, Entity Framework, xUnit. Tools & Infrastructure: Git, Docker, Azure, Azure DevOps, API GW, Datadog. Ability to work with a high level of autonomy and take full ownership of tasks. Strong self-management skills in an environment with no micro-management. C1 English level (both written and spoken). Nice-to-Have Skills: Familiarity with event-driven architectures or messaging systems (e.g., Azure ServiceBus). We