Regular .NET Developer (Card Payment Systems)

About the role We are looking for a Regular .NET Developer to join a team responsible for developing and maintaining core card payment systems - from transaction authorization and settlement to integrations with external payment services. The systems process hundreds of thousands of transactions daily, so performance, availability and security are key priorities. Work model: Remote-first with scheduled on-site team meetings (2 days per month in Warsaw).   Responsibilities - Develop and maintain .NET applications in card payment domain - Design and implement new functionalities according to business and regulatory requirements - Integrate systems with external services (REST, SOAP, messaging queues) - Optimize performance, availability and security of applications - Cooperate with Analysts, Architects and QA in Agile/Scrum teams - Participate in SIT/UAT testing, code reviews and preparation of technical documentation   Required skills - Commercial experience with C# and .NET (Framework / Core) - Experience with ASP.NET Core, Angular and WebAPI - Knowledge of Entity Framework, LINQ, Dapper - Experience with SQL Server (T-SQL) and query optimization - Knowledge of SOLID principles and design patterns - Experience writing unit tests (xUnit / NUnit) - Experience with system integrations (REST, SOAP, JSON, XML) - Experience working in Agile environment - Knowledge of Git, CI/CD and TeamCity   Language requirements - Polish: native or C2 level (required) - English: professional level enabling work with technical documentation   Nice to have - Experience in card payments / payment processing domain - Knowledge of Docker / Kubernetes - Experience working on high-availability or complex distributed systems   Margo Offers: - B2B cooperation - Remote working model - Benefits such as medical care and sports card - Co-financing trainings, certification exams and post-graduate studies - Ability to work in an international consulting company on ambitious projects - Possibility to get involved in outside-project activities with additional remuneration) - Excellent working atmosphere, integration events country: PL all locations: [Warsaw] commitment: Permanent contract & B2B department: Consulting location: Warsaw team: Polska Team