Sebastian Kalinowski, Full-stack Developer in Warsaw, Poland
Sebastian Kalinowski

Full-stack 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, and optimize existing systems.
Sebastian is now available for hire

Portfolio

Experience

Location

Warsaw, Poland

Availability

Part-time

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.

Employment

  • Senior .NET Developer

    2018 - PRESENT
    Santander Consumer Bank — Nordics
    • Designed and implemented an internal recurring task scheduler and tracker (front end and back end).
    • Designed and implemented a tax statement's administrative app using React (front end and back end).
    • Implemented back-end parts of the PSD2 directive (Consent, Cards).
    • Configured CI/CD pipelines in Azure DevOps and Octopus Deployment.
    • Ensured high quality of the project by proposing and implementing enhancements.
    • Maintained some internal projects.
    • Completed OAuth2 and OIDC configurational tasks.
    • Worked in scrum and scrum with kanban environments.
    • Served as an API Foundation team member—providing guidelines for organizing about API interfaces.
    Technologies: C#, JavaScript, .NET Core, React, TypeScript, REST, Azure
  • Senior .NET Developer

    2017 - 2018
    Citi
    • Redesigned components of the distributed batch system calculating the risk of G10 Rates trades.
    • Rearchitected and reimplemented critical component of an existing system which allowed slicing it and reducing its complexity.
    • Improved the existing codebase and paying off technical debt.
    • Investigated and solved non-trivial issues on daily basis.
    • Ensured high quality of the project by proposing and implementing enhancements.
    • Gave technical presentations for team members.
    Technologies: C#, .NET, RabbitMQ, Kafka, Couchbase, SQLServer
  • Senior Full-stack .NET Developer

    2016 - 2017
    KMD Poland
    • Developed new modules for the application for Danish utility companies supporting administration, billing, metering, task management (frontend and backend).
    • Implemented new features for the application supporting job center employees in Denmark (frontend and backend).
    • Ensured high quality of the project by proposing and implementing enhancements.
    • Worked in scrum.
    Technologies: C#, JavaScript, Web API, DB2, SQL, AngularJS, Azure, Angular
  • Senior .NET Developer

    2015 - 2016
    Grupa Pracuj
    • Implemented internal application supporting management of job offers for the largest recruitment platform in Poland.
    • Refactored flaws of current architecture.
    • Optimized performance of existing systems.
    • Ensured high quality of projects by proposing coding conventions, service contracts, code reviews and GitHub workflow in the team.
    • Mentored junior team members.
    • Worked in a scrum environment.
    Technologies: C#, JavaScript, Web API, Entity Framework, SQL Server, RabbitMQ, Akka.NET, AngularJS, NancyFx, CQRS
  • .NET Developer

    2014 - 2015
    mBank
    • Implemented currency exchange (FX) and payment basket modules for the mBank main website.
    • Built new modules for an existing corporate CRM, optimized existing code.
    Technologies: C#, JavaScript, WinForms, LINQ to SQL, SQL Server, ASP.NET MVC, jQuery
  • .NET Developer

    2011 - 2014
    EBR-IT
    • Implemented Idea4Work: an application that simplifies the management of programmatic projects.
    • Added new features to Deal Manager: a system that helps to manage a real estate agency in Australia.
    • Implemented projects like PalletPlus (asset management and tracking) and Document Control (versioning documents) for a customer from Australia.
    • Designed parts of the system (including architecture), creating reports and unit and integrated tests.
    • Applied domain-driven design (DDD), CQRS, and event sourcing patterns.
    • Coordinated a small team of three junior programmers.
    Technologies: C#, JavaScript, WPF, ASP.NET MVC, RavenDB, SQL, NServiceBus, Bootstrap, jQuery, Telerik Controls, Telerik Reporting, Kendo UI, Entity Framework
  • Junior .NET Developer

    2010 - 2011
    Pentegy
    • Implemented a certificate application for the Polish Office of Electronic Communications (e-learning, examination, and issuing certificates).
    • Adjusted and integrated existing open-source OCR/OMR software with the certificates app project.
    • Implemented the back end of mobile app for one of Ukrainian's banks.
    • Composed technical documentation.
    Technologies: C#, MySQL, Web Services, WCF, SQL Server, PHP

Experience

  • 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.

Skills

  • Languages

    C#, C#.NET, TypeScript, JavaScript, T-SQL, XAML, ECMAScript (ES6), CSS, HTML5, SQL, HTML
  • Frameworks

    .NET Core, .NET, Entity Framework Core, ASP.NET Core, OAuth 2, AngularJS, Kendo UI, ASP.NET
  • Other

    Full-stack, APIs, React.js, Windows Presentation Foundation (WPF), RESTful Microservices, Front-End Developer, Cloud, OpenID Connect (OIDC)
  • Libraries/APIs

    React, Entity Framework, WinForms, jQuery, NServiceBus
  • Tools

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

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

    Windows, Azure
  • Storage

    SQL Server 2016, RavenDB, MySQL

Education

  • 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

Certifications

  • PRINCE2 Foundation
    MAY 2014 - PRESENT
    PRINCE2®

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