Logo of Mariusz Kotas
Picture of Mariusz Kotas

Mariusz Kotas

Software Craftsman


Passionate pragmatic software developer from Czech Republic who is continuously improving software craftsmanship.

I'm an independent software freelancer/consultant. Don't hesitate to contact me if you have a custom solution you would like me to implement or help your team move forward.


I'm putting emphasis on a software quality and clean code. Interested in helping clients with their domain, focusing on solving their problems. I have great expertise in all .NET technologies.


  • Clean, pragmatic codebase
  • SOLID principles, TDD, design patterns
  • DDD, CQRS, Event sourcing
  • Microservices, REST, gRPC

.NET development

  • Perfect knowledge of C#
  • WPF, Windows Forms, ASP.NET MVC, WebAPI, UWP/WinRT
  • Entity Framework
  • Experience with DI containers, DevExpress, xUnit, NuGet and ReSharper
  • SSO - OpenID, OAuth (IdentityServer3/4)
  • Keeping up to date with .NET Core, EF Core, ASP.NET Core and cross platform development

Web frontend

  • Javascript, Typescript
  • SPA - Angular 2+, VueJS
  • ASP.NET MVC and WebAPI
  • GraphQL and REST API design


  • Good knowledge of SQL language
  • Experience with PostgreSQL, Microsoft SQL Server, SQLite and PL/SQL
  • Version control - SVN, Git
  • Continuous integration - TeamCity, Bamboo, Jenkins
  • Agile methodology - Scrum (Jira, Confluence), Kanban
  • Experience with functional programming paradigm (Haskell and F#)
  • Knowledge of Java, C++, Python
  • Bitcoin, cryptocurrencies and quantitative trading

Professional experience

IT Contractor

  • IT Contractor
  • Prague, Czech Republic
  • January 2017present

Software Engineer

  • Remote
  • April 2021present
  • Bitcoin and Lightning Network payments for everyone


  • A fully automated quantitative crypto trading desk

Solutions Architect & Tech Lead

  • Enterprise distributed system
  • .NET Core, Kubernetes

Senior Software Developer

  • Innovative projects
  • .NET Core, Angular 2

Software Developer

  • Hospital information system
  • Chemical process simulator
  • IS builder: framework for rapid development large information systems

Software Developer (C#)

  • Operating system for pensioner

Freelance projects

ERP system

  • Gigantic ERP system (150+ modules)
  • Microservices, horizontal scalability, greenfield project
  • Kubernetes, Linkerd, .NET Core, Angular, GraphQL, gRPC


  • Back-office system
  • Frontend: web application written in Angular 7, Ant design
  • Backend: .NET core, IdentityServer4, Hangfire
Screen of Nexus
Screen of Nexus
Screen of Nexus


  • Fast and optimized execution platform for our high-frequency trading (HFT) strategies
  • Reactive platform based on .NET core and Rx
Screen of TraXBot
Screen of TraXBot

Adnext Crypto

  • Crypto trading tools
  • Web application ASP.NET MVC + VueJS and SignalR (websockets)
Screen of Adnext Crypto
Screen of Adnext Crypto
Screen of Adnext Crypto

Primus Monitoring

  • Monitoring system for industrial washing machines
  • Desktop and web application (WinForms, ASP.NET MVC, DotVVM)
Screen of Primus Monitoring
Screen of Primus Monitoring
Screen of Primus Monitoring

Keyword Filter Application

  • Postprocessing for Google AdWords planner
  • Desktop application (WPF, Material design)
Screen of Keyword Filter Application
Screen of Keyword Filter Application
Screen of Keyword Filter Application

Projects & publications

Websocket client

    GitHub stars Nuget
  • Pure websocket client with built-in reconnection and error handling

Crypto websocket clients

    GitHub stars Nuget
  • Websocket connectors to various crypto exchanges
  • Bitfinex, Bitmex and Binance


  • Hobby project, the encryption app (Windows 10) for paranoid people


  • Open-source encryption portable library/wrapper for C#. It is used in commercial product Encryptor (see above).


  • Open-source library. Event aggregator / Message bus for .NET with plugins system support


  • Example of plugins system in the .NET world

Super Maze

  • Multiplatform game. It's created with the MonoGame framework (Open Source version of the XNA)

Issues of acquiring client data with touch-based interfaces

  • Bachelor thesis
  • Implementing touch-based web client for existing hospital IS


Applied informatics

  • Masaryk University, Faculty of Informatics
  • Brno, Czech Republic
  • Bachelor's degree programme
  • 20122014


    • Czech - Native or bilingual proficiency
    • Polish - Native or bilingual proficiency
    • English - Professional working proficiency

    Favorite books

    • Pragmatic Programmer (A. Hunt, D. Thomas)
    • Clean Code and Agile Principles, Patterns, and Practices (Uncle Bob)
    • Domain-Driven Design: Tackling Complexity in the Heart of Software (E. Evans)