Sebastian Kalinowski
Verified Expert in Engineering
Full-stack Developer
Warsaw, Poland
Toptal member since October 11, 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.
Portfolio
Experience
- T-SQL (Transact-SQL) - 10 years
- .NET - 10 years
- Full-stack - 10 years
- C# - 10 years
- JavaScript - 8 years
- React - 3 years
- TypeScript - 3 years
- .NET Core - 2 years
Availability
Preferred Environment
JetBrains Rider, Visual Studio Code (VS Code), Visual Studio, Windows
The most amazing...
...project I've worked on was a highly available risk calculation system processing transactions worth billions of dollars.
Work Experience
Senior .NET Developer
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.
Senior .NET Developer
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.
Senior Full-stack .NET Developer
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.
Senior .NET Developer
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.
.NET Developer
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.
.NET Developer
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.
Junior .NET Developer
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.
Experience
Scheduler and Workflow Service
Simpliciti
EasyEnergy
Education
Postgraduate Coursework in Project Management
Warsaw University of Technology - Warsaw, Poland
Master's Degree in Computer Science
Warsaw University of Technology - Warsaw, Poland
Bachelor's Degree in Computer Science
Warsaw University of Technology - Warsaw, Poland
Certifications
Azure Fundamentals
Microsoft
PRINCE2 Foundation
PRINCE2®
Skills
Libraries/APIs
React, Entity Framework, Windows Forms (WinForms), Web API, jQuery, NServiceBus
Tools
Visual Studio, ReSharper, C#.NET WinForms, JetBrains Rider, Telerik Reports, RabbitMQ, LINQ to SQL
Languages
C#, C#.NET, TypeScript, JavaScript, T-SQL (Transact-SQL), XAML, ECMAScript (ES6), CSS, HTML5, SQL, HTML, PHP
Frameworks
.NET Core, .NET, Entity Framework Core, Windows Presentation Foundation (WPF), ASP.NET Core, OAuth 2, Angular, NancyFx, ASP.NET MVC, Bootstrap, AngularJS, Kendo UI, ASP.NET
Paradigms
Agile, Scrum, Pair Programming, CQRS, Object-oriented Programming (OOP), REST
Platforms
Windows, Azure, Visual Studio Code (VS Code), Apache Kafka, Telerik
Storage
SQL Server 2016, Couchbase, Microsoft SQL Server, IBM Db2, RavenDB, MySQL
Other
Full-stack, APIs, RESTful Microservices, Front-end Development, Akka.NET, Controls, Web Services, Windows Communication Foundation (WCF), Cloud, OpenID Connect (OIDC)
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