Dennis is available for hire
Hire DennisDennis Keil
Verified Expert in Engineering
JavaScript Developer
Hamburg, Germany
Toptal member since December 30, 2019
Bio
Dennis is a senior software engineer with more than 10 years of development experience. He is an expert in full-stack development (C#, PHP, and Node.js, JavaScript, TypeScript, Angular, React, and Redux). Dennis also has experience with various types of databases such as MS SQL, MySQL, MongoDB, and Firebase.
Portfolio
Westnetz
React, Vite, Application State Management, Bunshi, React Router, Google Maps...
Fortune 100 North American Construction Equipment Manufacturer
Angular, JavaScript, CSS, HTML, Node.js, NgRx, Azure, Amazon Web Services (AWS)...
Bright Skies
Node.js, Entity Framework Core, ASP.NET, C#, Redux, React, TypeScript...
Experience
- TypeScript - 7 years
- JavaScript - 7 years
- C# - 5 years
- Angular - 5 years
- Node.js - 5 years
- React - 5 years
- ASP.NET MVC - 5 years
- React Native - 2 years
Preferred Environment
Slack, Visual Studio Code (VS Code), IntelliJ IDEA, React, Full-stack, CI/CD Pipelines, APIs, REST, MacOS, Node.js
The most amazing...
...thing I've developed is a highly customizable visualization platform for an energy management system.
Work Experience
Senior Full-stack Developer
2024 - 2026
Westnetz
- Contributed to the conception and design of complex front-end architecture using React 19 and Vite 8.
- Implemented automated tests for quality assurance with Playwright.
- Created reference architectures that serve as templates or guides for future projects.
Technologies: React, Vite, Application State Management, Bunshi, React Router, Google Maps, React Hook Form, REST, GraphQL, TypeScript, JavaScript, Tailwind CSS, CSS, Sass, Playwright, Vitest, React Testing Library, Git, GitLab, Scrum
Angular Developer
2020 - 2023
Fortune 100 North American Construction Equipment Manufacturer
- Developed web apps and apps for managing construction equipment.
- Tracked and fixed bugs with Azure Dev Ops as a reporting tool.
- Ensured high quality by writing unit and integration tests for all components.
Technologies: Angular, JavaScript, CSS, HTML, Node.js, NgRx, Azure, Amazon Web Services (AWS), NgRx/store, Linux, Single-page Applications (SPAs), PostgreSQL, Docker, Webpack, APIs, REST, RDBMS, Architecture, Ionic, Web Usability, API Integration
Senior Full-stack Developer
2019 - 2020
Bright Skies
- Developed a web application with highly dynamic forms using TypeScript and React in the front end and C# in the back end.
- Tracked and fixed bugs using Azure DevOps as a reporting tool.
- Ensured a stable application performance using automated tests.
Technologies: Node.js, Entity Framework Core, ASP.NET, C#, Redux, React, TypeScript, JavaScript, Front-end, Responsive Web Design (RWD), REST APIs, HTML5, CSS3, Linux, Single-page Applications (SPAs), Docker, Electron, Full-stack, Express.js, Webpack, CI/CD Pipelines, APIs, REST, RDBMS, Architecture, .NET, Material UI, Web Usability, DevOps, API Integration, Full-stack Development, .NET Core
Senior Full-stack Developer
2017 - 2018
E.ON
- Developed a highly customizable visualization platform for an energy management system using TypeScript and React in the front end and Node.js in the back end.
- Tracked and fixed bugs using Jira as the reporting tool.
- Configured automated application deployment using continuous integration and continuous delivery with GitLab CI.
Technologies: Scala, Redux, Angular, TypeScript, JavaScript, Front-end, Responsive Web Design (RWD), REST APIs, HTML5, CSS3, Linux, Single-page Applications (SPAs), Docker, Full-stack, Webpack, CI/CD Pipelines, APIs, REST, RDBMS, Architecture, React, Node.js, Web Usability, DevOps, API Integration, Full-stack Development
Senior Full-stack Developer
2016 - 2016
Foodist
- Created a Shopware extension for improving site and search performance.
- Customized the shop's front end using modern design guidelines for increased usability.
- Tracked and fixed bugs using Jira as the reporting tool.
Technologies: Algolia, Shopware, PHP, Front-end, Responsive Web Design (RWD), HTML5, CSS3, Linux, RDBMS, Web Usability, API Integration, Full-stack Development
Senior Full-stack Developer
2015 - 2016
Shelfsailor
- Developed a customer-to-customer marketplace for storage rooms.
- Customized landing pages to improve conversion rates.
- Implemented authentication through external services with OpenID.
Technologies: Ruby on Rails (RoR), TypeScript, JavaScript, Front-end, Responsive Web Design (RWD), REST APIs, HTML5, CSS3, Linux, RDBMS, Web Usability, Stripe API, API Integration, Full-stack Development
Senior Full-stack Developer
2012 - 2016
Dreamlines
- Developed a customer relationship management platform.
- Tracked and fixed bugs using Jira as the reporting tool.
- Deployed an on-premise infrastructure using CI/CD.
Technologies: Entity Framework, ASP.NET MVC, C#, AngularJS, TypeScript, JavaScript, Front-end, Responsive Web Design (RWD), REST APIs, HTML5, CSS3, Linux, Full-stack, RDBMS, SignalR, .NET, Web Usability, DevOps, API Integration, Full-stack Development, .NET Core
Full-stack Developer
2015 - 2015
Fashion Cloud
- Developed a B2B solution for storing product data for the fashion industry.
- Tracked and fixed bugs using Jira as the reporting tool.
- Created a front end for the management of product data and importing/exporting.
Technologies: MongoDB, Node.js, AngularJS, TypeScript, JavaScript, Front-end, Responsive Web Design (RWD), REST APIs, HTML5, CSS3, Linux, Single-page Applications (SPAs), Full-stack, Express.js, Web Usability, API Integration, Full-stack Development
Full-stack Developer
2012 - 2012
Makime Services
- Developed a social platform for connecting travelers.
- Migrated a database schema to improve site performance.
- Tracked and fixed bugs using Jira as the reporting tool.
Technologies: Symfony, PHP, JavaScript, Front-end, Responsive Web Design (RWD), HTML5, CSS3, PHP 7, Linux, Full-stack, API Integration, Full-stack Development
Experience
E.ON Optimum
E.ON Optimum is a highly customizable visualization platform for an energy management system. I worked on it as a full-stack developer in a team of about ten front-end and back-end developers. My main focus was to enable the end user to create customizable graphs and diagrams for his data, e.g., energy consumption or load peaks.
Game Companion App | AoE II Companion (Open Source)
https://aoe2companion.com/A React Native-based app providing match data and statistics for players of the game Age of Empires II: Definitive Edition. I was the lead developer. We built the front end using React Native with the cross-platform (iOS/Android) Expo Framework, React Native, and Redux. We built the back end in Node.js on AWS Lambda (Serverless) and Kubernetes at Digital Ocean. The website was built with Next.js.
Charade Game App | 59seconds
https://59seconds.app/I built a Flutter-based app similar to the game of charades for Android and iOS. The app features a modern UI and smooth 60 FPS animations. The back end uses a highly scalable Firebase database to enable multiplayer games.
Foodist
Foodist is a webshop for food products. I worked on it as a full-stack developer in a small team of three developers. Next to customizing the shop's front end, I created a shopware extension to improve the site and search performance greatly.
Fashion Cloud
https://www.fashion.cloud/Fashion Cloud is a B2B solution for storing product data for the fashion industry. I worked on it as a full-stack developer and in a small team of three developers, creating the Node.js and Angular-based web application from the ground up.
The Snake Online
https://github.com/denniske/the-snake-onlineA small Node.js-based app that manages a live streaming channel on Twitch.tv based on activity on a channel on the platform Mixer.com. For this purpose, it has access to both the Twitch and Mixer API.
Multi-HTTP Loader for NGX-Translate
https://github.com/denniske/ngx-translate-multi-http-loaderThis is an open-source plugin for NGX-Translate (an Angular localization library). It enables the application developer to aggregate localizations from multiple sources. I developed this project in my free time.
Abi-physik Education Portal
http://abi-physik.de/periodensystem-der-elementeI built a physics education portal for high school students. The back end was written in PHP. The site features many small interactive apps written in JavaScript/TypeScript. It also includes a periodic table with programmatically generated electron shell diagrams.
Education
2014 - 2016
Master's Degree in Computer Science
Hamburg University of Technology - Hamburg, Germany
2011 - 2014
Bachelor's Degree in Computer Science
Hamburg University of Technology - Hamburg, Germany
Skills
Libraries/APIs
Node.js, React, REST APIs, SignalR, Stripe API, Entity Framework, NgRx, NgRx/store, React Router, Google Maps, React Hook Form, Playwright, React Testing Library
Tools
Webpack, IntelliJ IDEA, Slack, Expo, Vitest, Git, GitLab
Languages
CSS, HTML, JavaScript, TypeScript, C#, PHP 7, HTML5, CSS3, Dart, GraphQL, Scala, PHP, Python, Sass
Frameworks
React Native, Next.js, ASP.NET MVC, Angular, Redux, Electron, Express.js, NestJS, Ionic, .NET, Material UI, .NET Core, Flutter, AngularJS, Ruby on Rails (RoR), Symfony, Entity Framework Core, ASP.NET, Tailwind CSS
Paradigms
Responsive Web Design (RWD), REST, DevOps, Agile Software Development, App Development, Scrum
Platforms
Vercel, Docker, Azure, Amazon Web Services (AWS), Linux, Windows, Visual Studio Code (VS Code), AWS Lambda, Kubernetes, Algolia, Firebase, MacOS, Android, iOS
Storage
RDBMS, PostgreSQL, MongoDB
Other
Single-page Applications (SPAs), APIs, Front-end, Full-stack, CI/CD Pipelines, Architecture, Web Usability, API Integration, Full-stack Development, Shopware, Web App Development, FastAPI, Vite, Application State Management, Bunshi
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