Karolis Stulgys, Developer in Vilnius, Vilnius County, Lithuania
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Karolis Stulgys

Bio

Karolis is a results-driven full-stack JavaScript engineer with over six years of experience in developing scalable web applications. He has proven expertise in modern JavaScript frameworks, API integrations, and cloud-based solutions. Karolis has a demonstrated ability to lead projects and deliver high-quality, maintainable code.

Portfolio

PEXX
JavaScript, TypeScript, React, Chakra UI, Next.js, CSSinJS...
Apart People AS
React, Node.js, Next.js, Front-end, Git, Figma, Artificial Intelligence (AI)...
All human
React, Next.js, Node.js, Proof of Concept (POC), Artificial Intelligence (AI)...

Experience

  • React - 7 years
  • Node.js - 7 years
  • Next.js - 5 years
  • JavaScript - 5 years
  • TypeScript - 5 years
  • Jest - 3 years
  • Cypress - 2 years
  • Prisma - 1 year

Preferred Environment

Slack, Visual Studio Code (VS Code), MacOS, Teams, Discord, Git, React, Node.js, Zoom, Chrome

The most amazing...

...tool I've developed is a web3 stablecoin payment gateway.

Work Experience

Lead Web Developer

2024 - PRESENT
PEXX
  • Handled project initiation and team leadership roles.
  • Spearheaded the development of pexx.com, overseeing project architecture and team recruitment.
  • Managed a team of five developers to deliver the platform two weeks ahead of schedule.
Technologies: JavaScript, TypeScript, React, Chakra UI, Next.js, CSSinJS, Amazon Web Services (AWS), Cypress, GraphQL, HTML, Jest, Node.js, PostgreSQL, React Native, Tailwind CSS, User Interface (UI), User Experience (UX), Responsive Design, Agile, Proof of Concept (POC), Artificial Intelligence (AI), Full-stack Development, Minimum Viable Product (MVP), API Integration, SQL, Front-end Development, Pixel Perfect, Responsiveness, Front-end, Full-stack, React Testing Library, Vite, Dashboards, Adyen Payments, Web3, Blockchain, Solana, Architecture, Technical Leadership, CI/CD Pipelines, Software Architecture, Responsive Web Design (RWD), Gemini API, Image Generation, OpenAI API, eCommerce, Content Management Systems (CMS), Headless CMS, Search Engine Optimization (SEO), Vercel, Apple Pay, Integration, Figma, Large Language Models (LLMs), CSS3, RESTFul APIs, React Hooks, UI Frameworks, Git, Unit Testing, Figma to React, Radix UI, TanStack Table, iOS, Android, Stripe, Firebase, Pinecone, REST APIs, Crypto, Pine Script, MUI CSS, UI Design, Web Development, Algorithms, Figma to HTML, Responsive UI, AI Integration, Affiliate Marketing API integration, ChatGPT, Agile Project Management, HubSpot, Express.js, SaaS, Startups, Anthropic, B2B, Google Sheets, Typeform, Looker Studio, Payment APIs, eCommerce Development, Server-side Rendering (SSR), Static Site Generators, AI Prompts, Agentic AI, Prompt Engineering, Retrieval-augmented Generation (RAG), AI Architecture, AI Automation, API Development, Cloud, REST, Fintech, Mobile Apps, Auth, Component-based Development, Payments

Front-end Developer

2025 - 2025
Apart People AS
  • Developed front-end UI components using React and Chadcn.
  • Integrated back-end APIs using NextJS and TypeScript.
  • Planned carefully and utilised LLMs (Claude code) for application development.
Technologies: React, Node.js, Next.js, Front-end, Git, Figma, Artificial Intelligence (AI), Large Language Models (LLMs), REST APIs, UI Design, Web Development, Real Estate, Algorithms, Figma to HTML, Responsive UI, AI Integration, Affiliate Marketing API integration, Supabase, ChatGPT, Supabase Auth, Agile Project Management, Agile, Express.js, SaaS, Startups, Shadcn, Anthropic, B2B, Google Sheets, Typeform, Looker Studio, Server-side Rendering (SSR), Static Site Generators, AI Prompts, Agentic AI, Prompt Engineering, Retrieval-augmented Generation (RAG), AI Architecture, AI Automation, API Development, Cloud, REST, Mobile Apps, Auth, Component-based Development, Payments

Web Developer

2021 - 2024
All human
  • Led the development of a comprehensive digital transformation for Irish Life, enhancing user experience and service delivery.
  • Implemented performance optimizations for Irish Life, resulting in a 25% increase in page load speed.
  • Collaborated on the redesign of An Post's online platform, improving accessibility and user engagement. Achieved a 30% reduction in bounce rate post-launch.
Technologies: React, Next.js, Node.js, Proof of Concept (POC), Artificial Intelligence (AI), Full-stack Development, Minimum Viable Product (MVP), API Integration, Front-end Development, Pixel Perfect, Responsiveness, Storybook, Front-end, Full-stack, Ant Design, Material UI, React Testing Library, Vite, Dashboards, Architecture, Technical Leadership, CI/CD Pipelines, Software Architecture, Responsive Web Design (RWD), Gemini API, Image Generation, OpenAI API, eCommerce, Content Management Systems (CMS), Headless CMS, Search Engine Optimization (SEO), Vercel, Apple Pay, Integration, Figma, Large Language Models (LLMs), CSS3, RESTFul APIs, React Hooks, UI Frameworks, Git, Unit Testing, Figma to React, Radix UI, TanStack Table, D3.js, Strapi, iOS, Android, Stripe, Firebase, Pinecone, REST APIs, Crypto, Azure, MUI CSS, Web Development, Algorithms, Figma to HTML, Responsive UI, AI Integration, Affiliate Marketing API integration, Supabase, ChatGPT, Supabase Auth, Agile Project Management, Agile, HubSpot, Express.js, Fastify, SaaS, Startups, Shadcn, B2B, Google Sheets, Typeform, Looker Studio, Web Scraping, Mobile eCommerce, Payment APIs, eCommerce Development, PostgreSQL, Server-side Rendering (SSR), Static Site Generators, AI Prompts, Agentic AI, Prompt Engineering, Retrieval-augmented Generation (RAG), AI Architecture, AI Automation, API Development, Cloud, REST, Image Processing, Fintech, Mobile Apps, Auth, Component-based Development, Payments

Software Engineer

2021 - 2022
TrustPilot
  • Developed and optimized integrations for platforms like Shopify, Wix, and Mailchimp, enhancing client onboarding efficiency by 20%.
  • Collaborated with a team of five engineers to deliver high-performance applications, reducing system latency by 15%.
  • Ensured the technical feasibility of UI/UX designs.
Technologies: React, TypeScript, Amazon Web Services (AWS), Node.js, JavaScript, Proof of Concept (POC), Artificial Intelligence (AI), Full-stack Development, Minimum Viable Product (MVP), API Integration, Front-end Development, Pixel Perfect, Responsiveness, Storybook, Front-end, Full-stack, React Testing Library, Dashboards, Responsive Web Design (RWD), Integration, Figma, Shopify, CSS3, RESTFul APIs, React Hooks, UI Frameworks, Git, Unit Testing, Figma to React, D3.js, REST APIs, MUI CSS, UI Design, Web Development, Algorithms, Figma to HTML, Responsive UI, SaaS, Startups, B2B, Web Scraping, Mobile eCommerce, Payment APIs, eCommerce Development, Server-side Rendering (SSR), Static Site Generators, API Development, Cloud, REST, Mobile Apps, Component-based Development, Payments

Web Developer

2020 - 2021
Netfront
  • Assisted with a wide range of design projects and met tight deadlines.
  • Developed pixel-perfect, functional, and responsive web UI.
  • Delivered high-quality production code using TypeScript, React and Redux, contributing to a 15% increase in application scalability.
Technologies: React, JavaScript, Typesafe, Full-stack Development, API Integration, Front-end Development, Pixel Perfect, Responsiveness, Front-end, Full-stack, React Testing Library, Responsive Web Design (RWD), Integration, Figma, CSS3, RESTFul APIs, React Hooks, UI Frameworks, Git, Strapi, REST APIs, Web Development, Algorithms, Responsive UI, Server-side Rendering (SSR), Static Site Generators, API Development, Cloud, REST

Software Engineer

2020 - 2021
Rocket
  • Led the modernization of a legacy enterprise desktop application to a web-based system,.
  • Decreased user-reported issues by 40% during the system migration and modernization.
  • Implemented Agile methodologies, improving sprint goal success rate by 25%.
Technologies: React, TypeScript, JavaScript, Node.js, Full-stack Development, API Integration, Front-end Development, Pixel Perfect, Responsiveness, Front-end, Full-stack, React Testing Library, Responsive Web Design (RWD), Integration, Figma, CSS3, RESTFul APIs, React Hooks, UI Frameworks, Git, REST APIs, Web Development, Algorithms, Responsive UI, API Development, Cloud, REST

Web Developer

2019 - 2020
UserCentric Pty Ltd
  • Designed and developed mobile-first, responsive web applications for enterprise clients, increasing mobile user engagement by 30%.
  • Implemented performance improvements, achieving a 20% faster page load speed.
  • Communicated with clients and designers UI/UX mockups.
Technologies: React, JavaScript, Node.js, Full-stack Development, API Integration, Front-end Development, Pixel Perfect, Responsiveness, Front-end, Ant Design, Material UI, React Testing Library, Responsive Web Design (RWD), Figma, CSS3, RESTFul APIs, UI Frameworks, Git, Strapi, REST APIs, Web Development, Algorithms, Figma to HTML, Responsive UI, Server-side Rendering (SSR), Static Site Generators, API Development, Cloud, REST

Experience

React Component Design System

I collaborated with designers and front-end developers while working on a React component design system used across many websites in the organization by front-end engineers. It was a great challenge to think through and implement a complex domain-driven, distributed design system.

Apps for eCommerce Platforms

Developed integration of TrustPilot app for biggest eCommerce platforms like Shopify, Square, and Wix. I worked as a full-stack developer in a fast-moving and delivering team of six developers, one PO, and one UI/UX designer.

POC Binary Options Trading App

Worked on POC (proof of concept) binary options trading app where clients can bid USD on USDT price change (up or down) in one min interval. I worked as a solo developer, communicating the app requirements directly with a client.

Crypto Payment Gateway for USDC and USDT Stablecoin Payments

https://eppy.io
Crypto Payment Gateway for USDC and USDT Stablecoin payments. The system accepts crypto payments with no intermediaries. Funds go directly to your wallet, secure, decentralized, and fast. Supported networks include Stellar, Solana, Tron, Base, Polygon, and Arbitrum.

Create PDFs and Images from HTML in Seconds

https://tailwindpdf.com
A tool to create PDFs from the browser using Tailwind CSS styles. This is a side project that I built for myself and other developers/designers. I built the UI, front end, and back end for this project, where users can submit HTML strings, and it will download a PDF.

Skills

Libraries/APIs

React, Node.js, Stripe API, React Testing Library, OpenAI API, TanStack Table, D3.js, Stripe, REST APIs, Typeform, API Development, Auth, CSSinJS

Tools

Git, Adyen Payments, Figma to HTML, ChatGPT, Shadcn, Google Sheets, AI Prompts, Prisma, Figma, Slack, Zoom

Languages

TypeScript, JavaScript, CSS, GraphQL, HTML5, CSS3, Pine Script, HTML, SQL

Frameworks

Next.js, Tailwind CSS, Remix, Ant Design, Material UI, MUI CSS, Express.js, Fastify, React Native, Jest, Cypress, ORMLite, Chrome

Paradigms

Agile, Responsive Web Design (RWD), Search Engine Optimization (SEO), Unit Testing, UI Design, Agile Project Management, B2B, REST, Component-based Development

Platforms

Visual Studio Code (VS Code), Firebase, Vercel, iOS, Android, HubSpot, Amazon Web Services (AWS), Blockchain, Shopify, Azure, MacOS, Typesafe

Storage

PostgreSQL, Cloud Firestore

Other

Responsive Design, Proof of Concept (POC), Artificial Intelligence (AI), Full-stack Development, Minimum Viable Product (MVP), API Integration, Front-end Development, Pixel Perfect, Responsiveness, Storybook, Front-end, Full-stack, Dashboards, Architecture, Technical Leadership, CI/CD Pipelines, Software Architecture, Gemini API, Image Generation, eCommerce, Content Management Systems (CMS), Headless CMS, Apple Pay, Integration, Large Language Models (LLMs), RESTFul APIs, React Hooks, UI Frameworks, Figma to React, Radix UI, Strapi, Web Development, Real Estate, Algorithms, Responsive UI, AI Integration, Affiliate Marketing API integration, Supabase, Supabase Auth, SaaS, Startups, Anthropic, Looker Studio, Web Scraping, Mobile eCommerce, Payment APIs, eCommerce Development, Server-side Rendering (SSR), Static Site Generators, Agentic AI, Prompt Engineering, Retrieval-augmented Generation (RAG), AI Architecture, AI Automation, Cloud, Image Processing, Fintech, Mobile Apps, Payments, User Interface (UI), User Experience (UX), HTML5 Animations, OpenAI, APIs, Vite, Web3, Solana, Pinecone, Crypto, Chakra UI, Gatsby, Teams, Discord, Convex

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