Publication
Unit Testing and Coding: Why Testable Code Matters
https://www.toptal.com/developers/qa/how-to-write-testable-code-and-why-it-matters
Sergey is available for hire
Hire SergeySergey Kolodiy
Verified Expert in Engineering
.NET Developer
Moscow, Russia
Toptal member since October 27, 2014
Bio
Sergey is a software engineer with extensive development experience in the .NET technology stack, with strong architecture and coding skills. He loves to work on complex and business-critical tasks with full involvement, high productivity, and great enjoyment. He is a big fan of clean, testable, and maintainable code and has worked on a number of successful projects ranging from small startups to complex enterprise applications.
Portfolio
Orthogonal
TypeScript, Max for Live, MIDI, State Machines, Jest, Unit Testing, Research...
Independent Project
C#, Telegram Bot API, Trading, Stock Price Analysis, .NET...
BoostLingo, LLC
JavaScript, C#.NET, AngularJS, .NET Core, Entity Framework Core, Web...
Experience
- C# - 15 years
- REST - 10 years
- Unit Testing - 10 years
- ASP.NET Web API - 9 years
- .NET Core - 8 years
- TypeScript - 3 years
- Microservices Architecture - 2 years
- Algorithmic Trading - 2 years
Preferred Environment
Git, Visual Studio, Windows, Microsoft Visual Studio, C#, C#.NET, Visual Studio Code (VS Code), Full-stack Development, GitHub, .NET Core
The most amazing...
...application I've created is a tool that generates an OData REST API and a single-page web UI for any relational SQL database.
Work Experience
Founder
2021 - PRESENT
Orthogonal
- Designed and developed a generative MIDI sequencer for Ableton Live, using Max for Live and Typescript, that allows users to create complex and varied musical patterns with minimal input.
- Launched and maintained a professional website for the product, using Docusaurus and React, that showcases its features, benefits, and pricing and provides a landing page for potential customers.
- Created and updated user documentation, including an installation guide, user manual, and getting started guides, using Docusaurus and React, that help users get started and use the product effectively.
- Managed and coordinated the work of external freelancers, who produced video overviews and voiceover instructions for video tutorials that demonstrate the product's functionality.
- Conducted and implemented manual and unit testing, user feedback, UI and UX research, and other quality assurance methods that improved the product's performance, usability, reliability, and customer satisfaction.
Technologies: TypeScript, Max for Live, MIDI, State Machines, Jest, Unit Testing, Research, Prototyping, UX Design, UI Design, CI/CD Pipelines, JSON, Obfuscation, Documentation, Docusaurus, AutoHotkey, C#, IT Project Management, React, API Development, Software Engineering
Software Engineer | Analyst
2019 - PRESENT
Independent Project
- Designed and developed a successful algorithmic trading solution.
- Implemented various data analytics algorithms and several trading strategies.
- Integrated the solution with Telegram bot API for remote management.
Technologies: C#, Telegram Bot API, Trading, Stock Price Analysis, .NET, Microsoft Visual Studio, ASP.NET Web API, Unit Testing, REST, LINQ, .NET Core, Algorithmic Trading, Object-oriented Programming (OOP), C#.NET, Azure, Microsoft Azure, SQL, APIs, Task Analysis, Visual Studio, Back-end, REST APIs, CI/CD Pipelines, Architecture, SOLID Principles, Dependency Injection, Inversion of Control (IoC), Markdown, Functional Programming, Object-oriented Design (OOD), SQL Server Management Studio (SSMS), Microsoft SQL Server, Design Patterns, Visual Studio Code (VS Code), Fiddler, Debugging, Mathematics, Software Architecture, Web API, API Integration, Agile, Web Development, Full-stack Development, Full-stack, GitHub, Solution Architecture, DevOps, Entity Framework, Performance, Back-end Architecture, Cloud Architecture, System Integration, Web Applications, Object-relational Mapping (ORM), Distributed Systems, Database Architecture, Data Structures, Cloud, Event-driven Programming, React, Event-driven Architecture, API Development, Software Engineering
Senior Software Engineer
2018 - 2022
BoostLingo, LLC
- Worked on new business-critical features in a fast-paced environment, fixed bugs, and refactored legacy code.
- Worked on all aspects of the system, including business logic workflows implementation, task analysis, third-party systems and services integration, back-end APIs and web client development, and much more.
- Made a performance audit and improved the performance of critical back-end APIs.
- Implemented a bunch of useful ASP.NET Core extensions and middleware, such as online user tracking and CSP handling.
- Achieved such exceptional project results with a Toptal client that I was bought out and started working with the client directly as a remote contractor.
Technologies: JavaScript, C#.NET, AngularJS, .NET Core, Entity Framework Core, Web, Twilio API, Twilio Programmable Video, Zoom, .NET, Microsoft Visual Studio, C#, ASP.NET Web API, Unit Testing, REST, LINQ, ASP.NET Core, Microsoft SQL Server, Scrum, Git, Object-oriented Programming (OOP), HTML, Azure, Microsoft Azure, SQL, APIs, Source Code Review, Code Review, Task Analysis, Visual Studio, Back-end, REST APIs, Architecture, SOLID Principles, Dependency Injection, Inversion of Control (IoC), Jira, Markdown, Functional Programming, Object-oriented Design (OOD), SQL Server Management Studio (SSMS), Refactoring, Design Patterns, Visual Studio Code (VS Code), Fiddler, Debugging, Mathematics, User Interface (UI), User Experience (UX), Front-end, Software Architecture, Web API, TypeScript, API Integration, Agile, Web Development, Full-stack Development, Node.js, Full-stack, GitHub, Solution Architecture, Angular, Windows Services, Entity Framework, Performance, Twilio, ASP.NET, IIS SQL Server, Back-end Architecture, Cloud Architecture, System Integration, SaaS, Web Applications, Object-relational Mapping (ORM), IdentityServer 4, Database Architecture, Cloud, React, Event-driven Architecture, Bootstrap, Amazon Web Services (AWS), API Development, Software Engineering
Senior Software Engineer
2017 - 2018
Shrader Group LLC
- Designed and implemented an ETL pipeline to migrate a large amount of data from a legacy Drupal-based system to the new SQL Azure database.
- Performed a codebase audit and fixed some serious issues related to security, database versioning, testability, and overall code quality.
- Made a performance audit and improved the performance of critical APIs up to ten times.
- Implemented continuous integration pipelines in VSTS.
Technologies: C#, .NET, Microsoft SQL Server, REST APIs, Entity Framework Core, ASP.NET Core, .NET Core, Data Integration, ETL, SQL Server Integration Services (SSIS), Microsoft Visual Studio, Unit Testing, REST, LINQ, Git, Object-oriented Programming (OOP), C#.NET, Azure, Microsoft Azure, SQL, APIs, Source Code Review, Code Review, Task Analysis, Visual Studio, Back-end, CI/CD Pipelines, Architecture, SOLID Principles, Dependency Injection, Inversion of Control (IoC), Microsoft Data Transformation Services (now SSIS), Object-oriented Design (OOD), SQL Server Management Studio (SSMS), Refactoring, Design Patterns, Visual Studio Code (VS Code), Fiddler, Debugging, Software Architecture, Web API, API Integration, Agile, Web Development, Full-stack Development, Full-stack, GitHub, Solution Architecture, DevOps, Entity Framework, Performance, IIS SQL Server, Back-end Architecture, Cloud Architecture, System Integration, SaaS, Web Applications, Object-relational Mapping (ORM), IdentityServer 4, Database Architecture, React, Data Mining, API Development, Software Engineering
Senior Software Engineer
2016 - 2017
FRONTSTEPS
- Implemented a centralized security token service and a granular permission-based authorization system for ASP.NET Core instead of coarse-grained role-based authorization.
- Implemented an automated voicemail system with voice recognition so homeowners can register their visitors by phone, and community guards will be immediately notified about new guest invitations.
- Built a notification API to deliver various notifications to the platform users.
- Implemented a bunch of useful ASP.NET Core extensions and middleware, such as a distributed cache with fallback logic.
- Worked on CI-related stuff, including continuous delivery pipelines and package management.
- Worked on payment systems integration, back-end APIs, web and desktop clients, and more.
Technologies: C#, .NET, Microsoft SQL Server, SendGrid, PubNub, Twilio, Identity Server, OAuth, Microservices, REST APIs, Entity Framework Core, ASP.NET Core, .NET Core, Microsoft Visual Studio, ASP.NET Web API, Unit Testing, REST, LINQ, Scrum, JavaScript, Git, Twilio API, Object-oriented Programming (OOP), HTML, C#.NET, Azure, Microsoft Azure, SQL, APIs, Source Code Review, Code Review, Task Analysis, Visual Studio, Back-end, CI/CD Pipelines, Architecture, SOLID Principles, Dependency Injection, Inversion of Control (IoC), Jira, Functional Programming, Object-oriented Design (OOD), SQL Server Management Studio (SSMS), Refactoring, Design Patterns, Visual Studio Code (VS Code), Fiddler, Debugging, Redis, Software Architecture, Web API, API Integration, Agile, Web Development, Full-stack Development, Full-stack, GitHub, Solution Architecture, Angular, Windows Services, DevOps, Entity Framework, Performance, ASP.NET, Back-end Architecture, Cloud Architecture, System Integration, SaaS, Web Applications, Object-relational Mapping (ORM), Distributed Systems, IdentityServer 4, Database Architecture, Cloud, Event-driven Programming, CSS, Event-driven Architecture, Bootstrap, API Development, Software Engineering
Senior Software Engineer
2014 - 2016
Infor
- Implemented an administration API with AWS integration for automatic code deployment.
- Created an administration REST service and AngularJS-powered single-page web application on top of it.
- Worked on new features, fixed bugs, and refactored legacy code.
Technologies: .NET, Moq, MSTest, Bootstrap, AngularJS, ASP.NET Identity, ASP.NET Web API, C#, Microsoft Visual Studio, Unit Testing, REST, LINQ, Microsoft SQL Server, Scrum, JavaScript, Object-oriented Programming (OOP), HTML, C#.NET, SQL, APIs, Source Code Review, Code Review, Task Analysis, Visual Studio, Back-end, REST APIs, Architecture, SOLID Principles, Dependency Injection, Inversion of Control (IoC), Jira, Functional Programming, Object-oriented Design (OOD), SQL Server Management Studio (SSMS), Refactoring, Design Patterns, Fiddler, Debugging, Front-end, Software Architecture, Web API, API Integration, Agile, Web Development, Full-stack Development, Full-stack, Windows Services, Entity Framework, Performance, ASP.NET, IIS SQL Server, Back-end Architecture, Cloud Architecture, System Integration, SaaS, Web Applications, Object-relational Mapping (ORM), Distributed Systems, Database Architecture, Cloud, Event-driven Programming, CSS, Event-driven Architecture, API Development, Software Engineering
Software Engineer
2014 - 2014
Freelance
- Implemented a web application for real-time server performance monitoring.
- Created a chart control with the D3.js library and helped the client avoid using commercial charting libraries.
- Implemented a REST API for one of the projects from scratch.
- Implemented an efficient parallel data parser for MediaWiki API.
Technologies: C#, .NET, Moq, MSTest, Bootstrap, D3.js, AngularJS, ASP.NET Web API, SignalR, ASP.NET, ASP.NET MVC, Microsoft Visual Studio, Unit Testing, REST, LINQ, JavaScript, Object-oriented Programming (OOP), HTML, C#.NET, SQL, APIs, Source Code Review, Code Review, Task Analysis, Visual Studio, Back-end, REST APIs, Architecture, SOLID Principles, Dependency Injection, Inversion of Control (IoC), Object-oriented Design (OOD), SQL Server Management Studio (SSMS), Microsoft SQL Server, Refactoring, Design Patterns, Fiddler, Debugging, Software Architecture, Web API, API Integration, Agile, NoSQL, Web Development, Full-stack Development, Full-stack, Performance, Back-end Architecture, Cloud Architecture, Web Applications, Database Architecture, Data Structures, CSS, API Development, Software Engineering
Senior Software Engineer
2013 - 2014
T-Systems International
- Implemented new functionalities and business logic for desktop and web applications.
- Helped integrate the software system with external services like SAP and others.
- Provided on-site application support and helped resolve issues on the customer's site.
- Helped to meet a bunch of important deadlines during the project's lifetime.
- Made a presentation on code review and best practices applicable to it.
Technologies: .NET, ASP.NET MVC, Entity Framework, C#, Microsoft Visual Studio, Unit Testing, REST, LINQ, ASP.NET Web API, Microsoft SQL Server, Scrum, JavaScript, Object-oriented Programming (OOP), HTML, C#.NET, SQL, APIs, Source Code Review, Code Review, Task Analysis, Visual Studio, Back-end, REST APIs, Architecture, SOLID Principles, Dependency Injection, Inversion of Control (IoC), Jira, Functional Programming, Object-oriented Design (OOD), SQL Server Management Studio (SSMS), Refactoring, Design Patterns, Fiddler, Debugging, Front-end, Software Architecture, Web API, API Integration, Agile, Web Development, Full-stack Development, Full-stack, Windows Services, Performance, ASP.NET, IIS SQL Server, Back-end Architecture, Cloud Architecture, System Integration, Web Applications, Object-relational Mapping (ORM), Database Architecture, CSS, API Development, Software Engineering
Software Engineer
2010 - 2013
ETNA Software
- Designed and developed a bunch of core system components: back-end APIs, services, and libraries for the sogotrade.com trading platform.
- Implemented and supported streaming and load balancing solutions for real-time market data delivery.
- Integrated back-end components with the customer's service monitoring system.
- Developed a market data provider with a web-based admin panel and AmiBroker integration.
- Introduced unit testing practices and testable code concepts to the project.
Technologies: .NET, Moq, MSTest, NUnit, ASP.NET MVC, Microsoft SQL Server, Entity Framework, C#, Microsoft Visual Studio, Unit Testing, REST, LINQ, Scrum, JavaScript, Object-oriented Programming (OOP), HTML, C#.NET, Java, SQL, APIs, Source Code Review, Code Review, Task Analysis, Visual Studio, Back-end, SOLID Principles, Dependency Injection, Inversion of Control (IoC), Functional Programming, Object-oriented Design (OOD), SQL Server Management Studio (SSMS), Refactoring, Design Patterns, Debugging, Mathematics, User Interface (UI), User Experience (UX), Front-end, MySQL, REST APIs, Web API, API Integration, Agile, NoSQL, Web Development, Full-stack Development, Full-stack, Windows Services, Performance, ASP.NET, IIS SQL Server, Back-end Architecture, Cloud Architecture, System Integration, SaaS, Web Applications, Object-relational Mapping (ORM), Database Architecture, Data Structures, CSS, Event-driven Architecture, Data Mining, API Development, Software Engineering
Experience
Flow: Generative MIDI Sequencer
https://orthogonal.one/products/flowFlow is a generative, non-linear MIDI sequencer for Ableton Live, built with Max for Live and TypeScript, that allows users to create complex and varied musical patterns with minimal input.
Flow uses state machines under the hood and allows users to compose music algorithmically by defining simple steps and rules that determine how the music will change over time. The user defines the rules, and Flow executes them, producing infinitely long and varying musical patterns.
Flow uses state machines under the hood and allows users to compose music algorithmically by defining simple steps and rules that determine how the music will change over time. The user defines the rules, and Flow executes them, producing infinitely long and varying musical patterns.
Boostlingo Platform
https://boostlingo.comThe Boostlingo platform unifies all the technology and workflow components necessary to support the management and coordination of customers interpretation related tasks, including on-site interpreter appointment scheduling, the management of on-demand and scheduled over-the-phone and video remote interpreting sessions, complete with all the ancillary business analytics and business administrative tools that customers need to get the job done.
Sogotrade.com Trading Platform
http://sogotrade.com/Sogotrade is a large-scale distributed platform for stock and options trading. It includes web and desktop client terminals and a set of powerful market research tools to help customers achieve their investing and trading goals.
ETNA Trader
https://www.etnasoft.com/etna-trader/ETNA Trader is a flagship all-in-one white label trading platform for online broker-dealers. It features a front office and back office and integrates with a variety of third-party services and exchanges.
ASPro
An enterprise software system for TÜV SÜD, a service corporation focusing on testing and certification in the industrial sector.
The system consists of two major parts: a desktop workstation for the technical inspection of cars and other vehicles and a web application for organizing drivers' license exams, surrounded by a set of back-end services and external systems.
The system consists of two major parts: a desktop workstation for the technical inspection of cars and other vehicles and a web application for organizing drivers' license exams, surrounded by a set of back-end services and external systems.
Infor Learning Management System
Infor Learning Management System is an enterprise SaaS solution for creating, delivering, and reporting on learning throughout customers' internal and extended organization. The goal of this solution is to replace complex processes, workflows, and systems with sophisticated yet intuitive technology.
PolyGen
https://github.com/sergey-kolodiy/PolyGenPolyGen is an open-source Roslyn-based code generator that produces an object-relational mapping layer using Entity Framework, REST API using ASP.NET Core Web API, and a user interface for a user-defined domain model.
Microsoft Certified Professional
Microsoft Certified Professional (MCP) certification validates IT professional and developer technical expertise through rigorous, industry-proven, and industry-recognized exams. MCP exams cover a wide range of Microsoft products, technologies, and solutions.
To validate the certification, use the following information:
Transcript ID: 1166968
Access Code: F4163941
To validate the certification, use the following information:
Transcript ID: 1166968
Access Code: F4163941
Functional Programming Principles in Scala
https://www.coursera.org/verify/TN47UQ4G6AThe Functional Programming Principles in Scala course introduces the cornerstones of functional programming using the Scala programming language. In this course, students discover the elements of the functional programming style and learn how to apply them usefully in their daily programming tasks, such as modeling business domains or implementing business logic.
Stack Overflow — Top 7% Overall
Stack Overflow is a place where developers and technologists go to gain and share knowledge.
Seventy-seven answers were given.
Active in C#, .NET, ASP.NET, ASP.NET Web API, Unit testing, and Entity Framework. Top 7% overall.
Seventy-seven answers were given.
Active in C#, .NET, ASP.NET, ASP.NET Web API, Unit testing, and Entity Framework. Top 7% overall.
Education
2005 - 2010
Bachelor's Degree in Information Systems and Technologies
Voronezh Institute of High Technologies - Voronezh, Russia
Certifications
SEPTEMBER 2015 - PRESENT
Microsoft Certified Professional
Microsoft
SEPTEMBER 2015 - PRESENT
Microsoft Specialist: Programming in C#
Microsoft
JULY 2014 - PRESENT
Functional Programming Principles in Scala
Coursera
Skills
Libraries/APIs
LINQ, Web API, React, API Development, Entity Framework, REST APIs, Moq, Node.js, SignalR, PubNub, SendGrid API, Twilio API, D3.js, Telegram Bot API
Tools
Visual Studio, Microsoft Visual Studio, GitHub, Azure DevOps Services, Git, Fiddler, Roslyn, Chrome Developer Tools, MSTest, SendGrid, Trello, Jira, Twilio Programmable Video, Zoom, AutoHotkey
Languages
Markdown, C#, JavaScript, C#.NET, Transact-SQL (T-SQL), HTML, SQL, TypeScript, Java, Scala, CSS
Frameworks
ASP.NET, .NET Core, ASP.NET Core, .NET, ASP.NET Web API, ASP.NET MVC, Angular, Entity Framework Core, Entity, NUnit, AngularJS, IdentityServer 4, Bootstrap, ASP.NET Identity, OAuth 2, Jest, Docusaurus
Paradigms
REST, Unit Testing, Object-oriented Programming (OOP), Dependency Injection, Object-oriented Design (OOD), Inversion of Control (IoC), Event-driven Architecture, Refactoring, Scrum, Microservices Architecture, Microservices, Functional Programming, Metaprogramming, Design Patterns, Azure DevOps, Agile, DevOps, Back-end Architecture, Object-relational Mapping (ORM), Event-driven Programming, ETL, Test-driven Development (TDD), Agile Software Development, UX Design, UI Design
Platforms
Visual Studio Code (VS Code), Azure, Twilio, Windows, Amazon Web Services (AWS), Web
Storage
Microsoft SQL Server, SQL Server Management Studio (SSMS), Redis, NoSQL, IIS SQL Server, Database Architecture, Data Integration, SQL Server Integration Services (SSIS), MySQL, JSON
Other
SOLID Principles, APIs, Task Analysis, Back-end, Architecture, Debugging, Web Development, Full-stack Development, Full-stack, Solution Architecture, Software Engineering, Code Auditing, Single-page Applications (SPAs), Identity Server, Algorithmic Trading, Microsoft Azure, Source Code Review, Code Review, CI/CD Pipelines, Mathematics, Software Architecture, Max for Live, API Integration, Windows Services, Performance, Cloud Architecture, System Integration, SaaS, Web Applications, Distributed Systems, Data Structures, Cloud, Data Mining, OWASP, OAuth, Performance Analysis, Microsoft Data Transformation Services (now SSIS), Domain-driven Design (DDD), Trading, Stock Price Analysis, User Interface (UI), User Experience (UX), Front-end, MIDI, State Machines, Research, Prototyping, Obfuscation, Documentation, IT Project Management
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