George is available for hire

George Sisko

Verified Expert in Engineering

Software Developer

North Athens, Greece

Toptal member since September 18, 2024

Expertise

Front-end Web Development GitHub React.js JavaScript REST API TypeScript Redux CSS Full-stack Node.js Angular GraphQL

Bio

George is a developer with over eight years of experience, specializing in React, Next.js, React Native, and Angular. He excels at developing robust and user-friendly interfaces for web and mobile applications, delivering the best possible results by mentoring others and maximizing team members' contributions. For the past four years, George has taught Vanilla JavaScript, React, Node.js, and GraphQL at a private college.

Portfolio

SAE Institute

JavaScript, React, MongoDB, Node.js, Front-end, Full-stack, Back-end, APIs...

HeyJobs

JavaScript, React, Next.js, TypeScript, Redux, Material UI, Cypress, Jest, RTL...

Bmpi

React, TypeScript, Zustand, Material UI, Jest, Storybook, JavaScript...

Experience

JavaScript - 6 years
React - 6 years
Redux - 5 years
TypeScript - 5 years
Jest - 5 years
Node.js - 4 years
React Native - 3 years
Next.js - 2 years

Availability

Part-time

Preferred Environment

GitHub, React, Next.js, Material UI, JavaScript, TypeScript, React Native, Redux, Zustand

The most amazing...

...projects I've participated in during my time at HeyJobs involved migrating several initiatives from React to Next.js.

Work Experience

Lecturer

2020 - PRESENT

SAE Institute

Discovered and introduced the JavaScript ecosystem along with other passionate colleagues.
Managed bi-weekly class modules for groups of nine students on average.
Conducted season material planning along with the Sector Director.

Technologies: JavaScript, React, MongoDB, Node.js, Front-end, Full-stack, Back-end, APIs, ECMAScript (ES6), GraphQL, REST, API Integration, Architecture, Technical Leadership, REST APIs, Responsive UI, Full-stack Development, Figma, Front-end Development, UI Components, Web App Development, Vite, GitHub

Front-end Engineer

2023 - 2025

HeyJobs

Migrated several initiatives from React to Next.js.
Created a request for comment (RFC) to migrate the Next.js pages router to the app router.
Prepared an RFC to migrate from Redux Toolkit to React Query.
Maintained and expanded the design system UI library, leveraging React, Material UI, and Storybook.
Supported the DevOps team in various technologies, including AWS, CircleCI, Sentry, and Datadog.
Developed a PoC for a mobile app with React Native Expo.

Technologies: JavaScript, React, Next.js, TypeScript, Redux, Material UI, Cypress, Jest, RTL, Storybook, CSS, HTML, CircleCI, Sentry, Datadog, Amazon Web Services (AWS), Amazon Cognito, Shadcn, Responsive UI, Tailwind CSS, Styled-components, SCSS, APIs, ECMAScript (ES6), Large-scale Projects, Front-end, API Integration, Architecture, Technical Leadership, React Redux, REST APIs, Testing, Unit Testing, Full-stack Development, Full-stack, React Native, Mobile Apps, Expo, Design Systems, Figma, Front-end Development, UI Components, Web App Development, Search Engine Optimization (SEO), React Query, GitHub

Front-end Engineer

2023 - 2023

Bmpi

Led the front-end department to redesign an existing reporting platform from scratch.
Handled the architectural design, development, and delivery of the MMP.
Provided mentoring and knowledge-sharing sessions for back-end development team members.

Technologies: React, TypeScript, Zustand, Material UI, Jest, Storybook, JavaScript, ECMAScript (ES6), Front-end, API Integration, Architecture, Technical Leadership, REST APIs, Testing, Unit Testing, Responsive UI, Design Systems, Figma, Front-end Development, UI Components, Web App Development, Ant Design, B2B, Vite, GitHub

Front-end Engineer

2022 - 2022

MdDS Reset

Migrated a static page to the existing React single page application project.
Led the front-end team to refactor an existing codebase.
Reviewed and improved the source code and implemented new features.

Technologies: React, TypeScript, Material UI, JavaScript, ECMAScript (ES6), Front-end, Responsive UI, Front-end Development, Web App Development, GitHub

Front-end Engineer

2021 - 2022

Avaloq

Migrated a core banking back-office platform from AngularJS to Angular 2.
Maintained, reviewed, and improved the existing migrated code.
Created new features and moved the app to the first minimum viable product (MVP).

Technologies: Angular, TypeScript, JavaScript, RxJS, NgRx, ECMAScript (ES6), Large-scale Projects, Front-end, API Integration, Responsive UI, Front-end Development, Web App Development, B2B

Front-end Engineer

2021 - 2021

Büro am Draht

Reviewed and improved the existing codebase for a German Ministry of Culture website.
Tracked and fixed bugs and performance issues along with the product manager.
Developed on-demand initiatives and made bug fixes until MVP delivery.

Technologies: React, JavaScript, Material UI, Strapi, ECMAScript (ES6), Front-end, API Integration, Responsive UI, Figma, Front-end Development, Web App Development

Full-stack Engineer

2019 - 2021

Dr Glinz Covis

Developed new features for a monorepo CRM web app for recruitment agencies.
Built new features for the codebase of a new product authorization web app.
Developed a new device management mobile app from scratch.

Technologies: JavaScript, React, MongoDB, Docker, CSS, TypeScript, Node.js, React Native, RxJS, Angular, NgRx, Express.js, GraphQL, Kubernetes, Redux, Redux-Saga, SCSS, Material UI, Zustand, Apollo, Apollo Client, Apollo Server, React Apollo, Front-end, Back-end, Full-stack, APIs, ECMAScript (ES6), REST, API Integration, Mobile Development, Architecture, React Redux, REST APIs, Testing, Unit Testing, Responsive UI, Mobile UI, Expo, React Native for Web, Mobile, Full-stack Development, Mobile Apps, Figma, Front-end Development, UI Components, Web App Development, B2B, React Query, GitHub

Front-end Engineer

2020 - 2020

BibeCoffee

Consulted with a team of two colleagues on architectural decisions regarding the codebase of a real-time coffee machine monitoring platform.
Mentored a team of two colleagues on a real-time monitoring platform for coffee machine usage.
Performed code reviews and improvements on an existing codebase until the MVP.

Technologies: Angular, RxJS, NgRx, SCSS, Material UI, ECMAScript (ES6), Front-end, API Integration, REST APIs, Responsive UI, Front-end Development, Web App Development

Front-end Engineer

2018 - 2019

Vodafone Innovus

Developed dashboard report features for IoT devices.
Improved the codebase and introduced unit test coverage.
Built an ASP.NET web service wrapper that consumed data from SOAP Java web services.

Technologies: JavaScript, RxJS, NgRx, C#, .NET, ASP.NET, Angular, Sass, Jest, APIs, ECMAScript (ES6), Large-scale Projects, Front-end, API Integration, REST APIs, Testing, Unit Testing, Responsive UI, Full-stack Development, Full-stack, Front-end Development, Web App Development, B2B

Front-end Engineer

2018 - 2018

Netcompany-Intrasoft

Developed a booking system web app for tennis courts from scratch.
Led a team of three junior front-end developers focused on architectural design.
Assisted the server-side back-end developers with API development.

Technologies: JavaScript, Angular, T-SQL (Transact-SQL), C#, ASP.NET, Sass, APIs, ECMAScript (ES6), Front-end, API Integration, REST APIs, Responsive UI, Full-stack Development, Full-stack, Front-end Development, Web App Development, B2B, GitHub

Junior Software Engineer

2017 - 2018

Relational

Developed a core banking management algorithm through a loan bookkeeping module.
Assisted business managers with database and infrastructure design.
Learned about new features and implemented them on the web application.

Technologies: JavaScript, CSS, jQuery, T-SQL (Transact-SQL), ASP.NET, WPForms, Ajax, Web MVC, APIs, Large-scale Projects, API Integration, Full-stack Development, Full-stack

Experience

HeyJobs | Job Platform

HeyJobs is an E2E job platform that connects recruiters and job seekers through a smooth and straightforward process. As part of a front-end team comprising six members, I contributed to various initiatives, primarily focusing on UX improvements and the migration from React to Next.js. Additionally, I actively worked on enhancing the developer experience and creating requests for comments (RFCs).

Skills

Libraries/APIs

React, React Redux, REST APIs, Node.js, React Native for Web, React Query, RxJS, NgRx, Redux-Saga, jQuery, Apollo Client

Tools

GitHub, Figma, Expo, CircleCI, Sentry, Amazon Cognito, Shadcn, React Apollo

Languages

JavaScript, TypeScript, CSS, HTML, ECMAScript (ES6), GraphQL, SCSS, C#, Sass, T-SQL (Transact-SQL)

Frameworks

Material UI, Redux, Jest, Next.js, React Native, Cypress, Angular, Tailwind CSS, Express.js, .NET, ASP.NET, Ant Design

Paradigms

Testing, Unit Testing, B2B, REST, Mobile Development, Search Engine Optimization (SEO)

Platforms

Mobile, Docker, Kubernetes, Amazon Web Services (AWS)

Storage

MongoDB, Datadog

Other

Styled-components, Responsive UI, Front-end, APIs, API Integration, Design Systems, Front-end Development, UI Components, Web App Development, Vite, Zustand, RTL, Storybook, Full-stack, Full-stack Development, Large-scale Projects, Architecture, Technical Leadership, Mobile UI, Mobile Apps, Strapi, WPForms, Ajax, Web MVC, Apollo, Apollo Server, Back-end

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