Grzegorz is available for hire

Grzegorz Marzencki

Verified Expert in Engineering

JavaScript Developer

Location

Kraków, Poland

Toptal Member Since

June 23, 2021

Grzegorz has experience leading teams and working as a CTO. He is an expert JavaScript developer and trainer with expertise in front-end architecture design and team leadership. He has delivered projects for startups (including an MVP that won business funding) and large tech companies like Microsoft, MongoDB, and Two Sigma. Grzegorz's strengths are team leadership, building scalable architectures, and delivering the highest quality code.

Software Engineering Software Front-end Web Development User Interface (UI)Third-party APIs JavaScript CSS WebApp TypeScript Web Architecture HTML5 Less Sass REST APIs

Portfolio

Freelance

Angular, AngularJS, React, Node.js, JavaScript Testing, JavaScript...

jstrainings.com

Angular, React, Node.js, JavaScript, JavaScript Testing, CSS, HTML, TypeScript...

Codete

JavaScript, Angular, React, AngularJS, Team Management, Webpack, CSS, HTML...

Experience

JavaScript - 9 years REST APIs - 6 years Team Management - 5 years Technical Leadership - 5 years React - 4 years RxJS - 4 years Angular - 4 years Next.js - 2 years

Availability

Part-time

Preferred Environment

WebStorm

The most amazing...

...product I've delivered was an MVP for a startup that got the company funding. I was later hired to build the development team from the ground up.

Work Experience

JavaScript Developer and Architect

2016 - PRESENT

Freelance

Assisted startups and FAANG companies as an architect, tech lead, and developer.
Designed front-end architecture and oversaw the entire delivery process (from idea to solution).
Led teams of designers and developers and worked closely with project owners.

Technologies: Angular, AngularJS, React, Node.js, JavaScript Testing, JavaScript, Team Management, CSS, HTML, TypeScript, MongoDB, REST, Webpack, Architecture, Web Architecture, Leadership, API Architecture, Technical Leadership, Third-party APIs, Third-party Integration, Accessibility, RxJS, GraphQL, Front-end, Front-end Architecture, Web Development, User Experience (UX), API Integration, User Interface (UI), WebApp, Startups, HTML5, CSS3, Sass, SCSS, Material Design, Software Architecture, NgRx, Redux, APIs, Team Leadership, Software Engineering, CTO, Front-end Development, ECMAScript (ES6), Next.js, NestJS, Software, Firebase, Amazon Web Services (AWS)

JavaScript Trainer

2015 - PRESENT

jstrainings.com

Delivered around 1,000 hours of technical training about JavaScript and web technologies.
Created training for people from companies such as (but not limited to): Orange, Ericsson, Nordea, and Comarch.
Authored a video course for Packt Publishing about JavaScript.

Technologies: Angular, React, Node.js, JavaScript, JavaScript Testing, CSS, HTML, TypeScript, MongoDB, REST, Webpack, Architecture, Web Architecture, Leadership, API Architecture, Technical Leadership, RxJS, Front-end, Front-end Architecture, Web Development, User Experience (UX), API Integration, User Interface (UI), WebApp, HTML5, CSS3, Software Architecture, APIs, Software Engineering, Front-end Development, ECMAScript (ES6), Software, Next.js

Senior JavaScript Developer

2015 - 2016

Codete

Developed an MVP in Angular for a German startup (video platform).
Redesigned architecture and implemented from scratch an enterprise application with migration from jQuery legacy code to React and Redux, ES6, Immutable.js, and Webpack.
Conducted a number of technical interviews for a JavaScript-related position.
Developed the enterprise application for a Norwegian company (AngularJS).

Technologies: JavaScript, Angular, React, AngularJS, Team Management, Webpack, CSS, HTML, TypeScript, REST, Architecture, Web Architecture, Leadership, API Architecture, Technical Leadership, Third-party APIs, Third-party Integration, RxJS, JavaScript Testing, Front-end, Front-end Architecture, Web Development, API Integration, User Interface (UI), WebApp, Startups, HTML5, CSS3, Sass, SCSS, Material Design, Software Architecture, Redux, APIs, Team Leadership, Software Engineering, D3.js, Front-end Development, ECMAScript (ES6), Software

Software Developer

2014 - 2015

Grape Up

Mentored the front-end team (German startup) to redesign AngularJS architecture.
Introduced AngularJS to the team of Apache Flex developers.
Created a set of internal tools for fast project setup.

Technologies: JavaScript, AngularJS, CSS, HTML, REST, Third-party APIs, Third-party Integration, Front-end, Web Development, API Integration, User Interface (UI), WebApp, CSS3, Less, Software Architecture, Redux, APIs, Software Engineering, Front-end Development, Software

Co-founder

2012 - 2013

Young Da Vinci

Created the company from scratch, including product prototyping, and hiring.
Prepared and conducted a number of courses on programming dedicated to youngsters.
Prepared and conducted a number of lectures for students.

Technologies: Team Management, Leadership, Startups, Software Engineering, Front-end Development, Software

Experience

Security Management System for High-risk Areas

https://jstrainings.com/security_system/video.html

Developed the prototype of a system (MVP for a startup) and led a team in developing a fully functional product. The project was a security monitoring system providing a dashboard for real-time management of devices placed in hazardous areas. The solution was based on RX streams.

Skills

Languages

JavaScript, TypeScript, CSS, HTML, CSS3, HTML5, Less, Sass, SCSS, ECMAScript (ES6), GraphQL

Frameworks

Angular, WebApp, Next.js, Redux, Bootstrap, NestJS, Tailwind CSS, AngularJS

Libraries/APIs

React, RxJS, REST APIs, Node.js, NgRx, D3.js

Tools

JavaScript Testing, WebStorm, Webpack

Paradigms

REST, Web Architecture, API Architecture, Management

Other

Team Management, Architecture, Leadership, Technical Leadership, Third-party APIs, Third-party Integration, Front-end, Front-end Architecture, Web Development, API Integration, User Interface (UI), Material Design, Software Engineering, Team Leadership, APIs, Software Architecture, Front-end Development, Software, User Experience (UX), Startups, CTO, GPT, OpenAI GPT-4 API, OpenAI GPT-3 API, Accessibility

Platforms

Firebase, Amazon Web Services (AWS)

Storage

MongoDB

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