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