Grzegorz Marzencki
Verified Expert in Engineering
JavaScript Developer
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.
Portfolio
Experience
- JavaScript - 9 years
- Team Management - 5 years
- Technical Leadership - 5 years
- React - 4 years
- Angular - 4 years
- Next.js - 2 years
- Artificial Intelligence (AI) - 1 year
- Large Language Models (LLMs) - 1 year
Availability
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
Founding Engineer
Codemod
- Developed a tool that leverages AI to generate error-free code transformations by analyzing before-and-after code pairs and providing step-by-step progress updates.
- Oversaw the development of AI-related code using Python and OpenAI technologies.
- Handled both front-end and back-end code development.
Advisor
PEACHTREE SPINE PHYSICIANS, INC.
- Implemented a proof of concept (POC) of a new architecture incorporating a headless CMS.
- Reviewed project prompts for communication with large language models to align with client needs.
- Audited the client's code and provided guidance on the next steps in product development.
Senior Web Engineer
MongoDB
- Rebuilt an existing webpage using TypeScript and Next.js, resulting in a Google performance score increase from 38% to 98%.
- Built a service from scratch as a proof of concept for architecture that was later implemented in MongoDB's new web application.
- Achieved scalability by creating generic, composable components and established modularity using Atomic Design principles.
Interim CTO
Reconstruction US Inc.
- Served as a team leader, managed the team's workload, prepared tasks, and oversaw talents.
- Reframed the vision for technology and rebuilt the tech stack entirely.
- Created strategies to hire excellent developers, which increased the velocity of the technical work by 10x.
- Worked closely with the business team to create products well aligned with the business needs.
Senior Software Engineer
Microsoft
- Contributed to the PowerBI, one of Microsoft's flagship projects.
- Implemented a new architecture (based on reactive streams) to enhance features and user experience.
- Build UI with a strong focus on accessibility and scalable infrastructure.
JavaScript Trainer
jstrainings.com
- Delivered around 1,000 hours of technical training in JavaScript and web technologies.
- Created training for people from companies such as Orange, Ericsson, Nordea, Comarch, and more.
- Authored a video course about JavaScript for Packt Publishing.
Senior JavaScript Developer
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).
Software Developer
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.
Co-founder
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.
Experience
Security Management System for High-risk Areas
https://jstrainings.com/security_system/video.htmlSkills
Libraries/APIs
React, RxJS, REST APIs, Node.js, NgRx, OpenAI API, D3.js
Tools
JavaScript Testing, WebStorm, Webpack, Terraform, Grafana, Prisma, AI Prompts, Docker Compose
Languages
JavaScript, TypeScript, CSS, HTML, CSS3, HTML5, Less, Sass, SCSS, ECMAScript (ES6), Python 3, GraphQL, Python
Frameworks
Angular, WebApp, Next.js, Tailwind CSS, Material UI, Redux, Bootstrap, NestJS, AngularJS, Serverless Framework
Paradigms
REST, Web Architecture, API Architecture, MEAN Stack, Management, Serverless Architecture
Storage
MySQL, MongoDB, Amazon S3 (AWS S3), Redis
Platforms
Firebase, Amazon Web Services (AWS), Kubernetes, Docker, AWS Lambda, Azure
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, MERN Stack, Full-stack, Single-page Applications (SPAs), Storybook, Design Systems, UI Components, Tailwind UI, User Experience (UX), Startups, CTO, Generative Pre-trained Transformers (GPT), OpenAI GPT-4 API, OpenAI GPT-3 API, OpenAI, Large Language Models (LLMs), Machine Learning, Planning, Full-stack Development, Prompt Engineering, Generative Artificial Intelligence (GenAI), Atomic Design, Radix UI, Fractional CTO, Accessibility, Artificial Intelligence (AI), Prometheus, Serverless, Education Technology (Edtech), FastAPI, Headless CMS, ChatGPT Prompts
How to Work with Toptal
Toptal matches you directly with global industry experts from our network in hours—not weeks or months.
Share your needs
Choose your talent
Start your risk-free talent trial
Top talent is in high demand.
Start hiring