Sebastian Kalinowski, Software Developer in Warsaw, Poland
Sebastian Kalinowski

Software Developer in Warsaw, Poland

Member since May 10, 2019
Sebastian is a .NET developer specializing in back-end layer development. He has over a decade of professional experience within banking, financial, and recruitment industries. He’s also comfortable in front-end development (React), system design, and architecture. Sebastian has successfully worked with numerous clients to define requirements, design new system elements, implement new functionalities as well as optimize existing systems.
Sebastian is now available for hire




Warsaw, Poland



Preferred Environment

Windows, Visual Studio, Visual Studio Code, Rider

The most amazing...

...project I've worked on was a highly available risk calculation system processing transactions worth billions of dollars.


  • Senior .NET Developer

    2018 - PRESENT
    Santander Consumer Bank — Nordics
    • Implemented internal systems used by other development teams.
    • Created a scheduler and recurring task execution tracker (the UI was built in React).
    • Constructed parts of the PSD2 directive.
    • Communicated in English on a daily basis concerning refine documentation and design.
    • Worked within the Scrum methodology.
    Technologies: C#, .NET Core, React, TypeScript, REST
  • Senior .NET Developer

    2017 - 2018
    • Worked on a batch system calculating the risk of G10 Rates trades.
    • Redesigned components of the system.
    • Implemented features according to internal/gathered requirements and needs.
    • Mentored other team members by giving internal presentations.
    • Communicated in English on a daily basis.
    Technologies: C#, .NET, RabbitMQ, Kafka, Couchbase, SQLServer
  • Senior Full-stack .NET Developer

    2016 - 2017
    KMD Poland
    • Developed an application for utility companies supporting administration, billing, metering, and task management.
    • Created an application that supported job center employees in Denmark.
    • Implemented features according to internal requirements and needs.
    • Communicated in English on a daily basis concerning refine documentation and design.
    • Worked in a Scrum environment.
    Technologies: C#, Web API, DB2, SQL, AngularJS, Azure, Angular
  • Senior .NET Developer

    2015 - 2016
    Grupa Pracuj
    • Developed an application supporting creating new job offers (internal, customer care, and sales).
    • Built the core service responsible for publishing offers on
    • Refactored flaws of the current architecture, optimizing the performance of existing systems.
    • Mentored other team members.
    • Introduced coding conventions, contracts, code review, and a GitHub workflow in the team.
    • Took part in domain discussion meetings.
    Technologies: C#, Web API, Entity Framework, SQL Server, RabbitMQ, Akka.NET, AngularJS, NancyFx, CQRS
  • .NET Developer

    2014 - 2015
    • Developed a corporate CRM (new features).
    • Built a new mBank page (currency exchange, and payments basket).
    • Implemented features according to the client’s requirements and needs.
    • Designed new parts of the system and optimized the existing ones (CRM).
    • Communicated regularly with internal customers.
    Technologies: C#, WinForms, LINQ to SQL, SQL Server, ASP.NET MVC, jQuery
  • .NET Developer

    2011 - 2014
    • Developed Idea4Work: an app that simplifies the management of programmatic projects.
    • Built Deal Manager: a system that helps to manage a real state agency (a client from Australia).
    • Created PalletPlus (an app for asset management and tracking) and document control (versioning documents).
    • Communicated daily with customers (mainly in English).
    • Designed parts of the system (including architecture) and created reports, unit, and integration tests.
    • Applied domain-driven-design (DDD), CQRS, and event-sourcing patterns.
    • Coordinated a small team of three programmers.
    Technologies: C#, WPF, ASP.NET MVC, RavenDB, SQL, NServiceBus, Bootstrap, jQuery, Telerik Controls, Telerik Reporting, Kendo UI, Entity Framework
  • Junior .NET Developer

    2010 - 2011
    • Implemented various certificates for the Office of Electronic Communications (including e-learning, certification, issuing certificates, and more).
    • Developed an iOS banking app for one of the Ukrainian banks (back end).
    • Adjusted the existing OCR/OMR software for the certificates project.
    • Created and translated technical documentation.
    Technologies: C#, MySQL, Web Services, WCF, SQL Server, PHP


  • Scheduler and Workflow Service (Development)

    An internal project used by other developer teams for scheduling and execution tracking of recurring tasks. The project was built on top of one of the open-source schedulers and .NET Core in RESTful microservices architecture with a front end built with React and TypeScript.

  • Simpliciti (Development)

    This was an internal project that involved a complex batch system calculating the risk of G10 Rates trades. The system had to be highly available and work 24/7. The project was built using .NET, RabbitMQ, SQL Server, and Couchbase. Since the build of the project, I've added new features and refactored one of the critical components.

  • EasyEnergy (Development)

    This is an application for utility companies that supports administration, billing, metering, and task management. The project was supposed to replace some small legacy WinForms applications with one, coherent application built with AngularJS. The back end was built with the .NET framework and DB2 as a persistence layer.


  • Languages

    C#, TypeScript, JavaScript, T-SQL
  • Frameworks

    .NET Core, .NET, Entity Framework Core, ASP.NET Core 2, AngularJS, Kendo UI, ASP.NET
  • Libraries/APIs

    TensorFlow, React, Entity Framework, jQuery, NServiceBus
  • Other

    Front-End Developer, Windows Presentation Foundation (WPF), RESTful Microservices
  • Tools

    Visual Studio, ReSharper, C#.NET WinForms, RabbitMQ, LINQ to SQL
  • Paradigms

    Agile, Scrum, Pair Programming, CQRS, Object-oriented Programming (OOP), REST
  • Platforms

  • Storage

    SQL Server 2016, RavenDB


  • Postgraduate coursework in Project Management
    2013 - 2014
    Warsaw University of Technology - Warsaw, Poland
  • Master's degree in Computer Science
    2011 - 2012
    Warsaw University of Technology - Warsaw, Poland
  • Bachelor's degree in Computer Science
    2007 - 2011
    Warsaw University of Technology - Warsaw, Poland
  • PRINCE2 Foundation
    MAY 2014 - PRESENT

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