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Szymon – React, Node.js, Next.js, experts in Lemon.io

Szymon

From Poland (GMT+2)

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Full-stack Web DeveloperMiddle-to-senior
Hire developer
7 years of commercial experience
Accounting
Advertising
AI
Banking
Computer science
Cryptocurrency
Data analytics
Event management
Healthcare
Machine learning
Printing
Product management
Public relations
AI software
CMS
CRM
Customer support software
Mobile apps
Platforms
SaaS
Web3
Lemon.io stats
2
projects done
1168
hours worked
2
offers now 🔥

Szymon – React, Node.js, Next.js

Meet Szymon - a Strong Middle Full-stack Web Developer! Besides being an experienced developer, he performs well in client-facing situations. Szymon is polite, able to explain his way of thinking in a non-technical way, can think out of the box, and can listen and improve based on received feedback. His experience spans business domains like education, web3, events, trading, and many more.

Main technologies
React
4 years
Node.js
4.5 years
Additional skills
Next.js
Blockchain
Solidity
JavaScript
Python
MySQL
NoSQL
ElasticSearch
AWS
Tensorflow
Apache Airflow
Tailwind CSS
Docker
Firebase
NLP
Web 3.0
C++
Kotlin
React Native
MongoDB
PostgreSQL
OpenAI
Tensorflow
AI
Shopify
Typescript
liquid
Vercel
shadcn
Hono.js
Cloudflare Worker
Ready to start
ASAP
Direct hire
Potentially possible

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Experience Highlights

Lead Full-stack Engineer
Apr 2024 - Oct 20246 months
Project Overview

This is a benefit system for employees and a way for employers to lower their taxes. From the employers' side, it's a complex CRM with the ability to see tens of thousands of records in a table, create two different merchant accounts with two different dashboards, and synchronize its state with blockchain to meet legal requirements. From the employees' standpoint, it's a mobile app where they can send back tokens and get different benefits in exchange.

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Responsibilities:
  • Designed and optimized a scalable PostgreSQL (pSQL) database, enabling the system to handle tens of thousands of requests per second for rapid response times;
  • Developed a smart contract and accompanying service to mirror transactions on the blockchain, ensuring transparency for legal reasons;
  • Implemented Next.JS 14 with server and client-side architecture, achieving optimal performance;
  • Built a mobile app using React Native for Android and iOS;
  • Developed a responsive CRM interface that efficiently displays thousands of data rows without lag, enabling real-time insights.
Project Tech stack:
AI
Next.js
PostgreSQL
Typescript
Blockchain
Polygon
Solidity
React Native
Lead Full-stack Engineer
Jun 2023 - Jan 20247 months
Project Overview

A membership app for the major Polish fitness influencer. What started as a simple membership app project with workout videos, quickly grew in functionality to soon include also e-commerce, CRM for salespeople who called abandoned carts (surprisingly profitable), testing and optimizing paywall with superwall, etc.

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Responsibilities:
  • Deployed a Flutter app to Web, iOS & Android;
  • Built the full e-commerce stack - email follow-ups, customer journey, shipping;
  • Scaled the app to 5k users and $30k / mo revenue while maintaining 98% uptime;
  • Integrated Stripe & Revenucat - subscription & product payments;
  • Did A/B Testing for paywalls to maximize revenue.
Project Tech stack:
Flutter
Firebase
Stripe API
AI
Full Stack Developer
May 2023 - Sep 20233 months
Project Overview

Built a custom Shopify app to streamline order management for a growing e-commerce business.

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Responsibilities:
  • Designed and built a private Shopify app using Node.js and React to provide advanced order management features directly within the Shopify admin panel.
  • Integrated the app with third-party APIs (e.g., shipping providers, payment gateways) using Shopify Admin API and GraphQL, enabling automated tracking updates and real-time order status syncing.
  • Implemented robust filtering, sorting, and reporting features with React Table and Chart.js, providing the client with actionable insights into their sales and fulfillment processes.
  • Utilized Shopify Webhooks to handle real-time order updates and sync changes seamlessly, ensuring data accuracy across all systems.
  • Deployed the app on AWS with Docker and implemented OAuth-based authentication for secure access across multiple stores.
Project Tech stack:
liquid
JavaScript
AJAX
Ruby
Lead Full-stack Engineer
Mar 2023 - Jun 20232 months
Project Overview

A research, psychology Single Page Application game to test user reaction times and feed the data to an AI algorithm.

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Responsibilities:
  • Created responsive frontend gaming experience using NextJS;
  • Implemented PyTorch to teach the algorithm about user behavior;
  • Implemented backend in Python.
Project Tech stack:
Next.js
AI
Lead Full-stack Developer
Jun 2022 - Feb 20238 months
Project Overview

It's a product that provides web2 companies with web3 capabilities, allowing them to airdrop NFTs to customers with simple API commands, as well as a professional dashboard where they can track activity. It comes with payments support and multi-chain support.

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Responsibilities:
  • Took the product from ideation to MVP;
  • Managed a team of 2 other Full-Stack developers;
  • Introduced fast iterations, due to CI/CD process that I've designed;
  • Implemented multi-chain support, including Solana;
  • Created custom Custodial Wallet solution using AWS and MPC cryptography.
Project Tech stack:
Next.js
Prisma
Tailwind CSS
Nest.js
Solidity
Rust
HardHat
Back-end Developer
Sep 2021 - May 20228 months
Project Overview

Crypto currency service, which works similarly to Stack Overflow, with that difference, that for valuable answers, you get pay in crypto, and all of the content is translated into all of the supported languages.

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Responsibilities:
  • Introduced the mechanism to translate content to all languages in the world and display appropriate content depending on location/user preferences;
  • Performed NLP processing;
  • Implemented Elastic search to provide extra fast search recommendations.
Project Tech stack:
Python
ElasticSearch
NLP
Web 3.0
Full-stack Developer
Nov 2021 - May 20226 months
Project Overview

General application for event management, ticket creation, dynamically generating iframes for sharing, and payments management.

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Responsibilities:
  • Created complex frontend with Next.js & chart.js;
  • Created a fully responsive design;
  • Integrated Stripe Payments;
  • Added SQL database with Prisma;
  • Added the ability to share events as iframes.
Project Tech stack:
Next.js
MySQL
Stripe API
Prisma
Serverless Computing
Full-stack Developer
Jul 2021 - Nov 20213 months
Project Overview

Application for covid tests management in restaurants. The whole process of making a covid test was integrated into an app, along with an AI algorithm that was checking the covid test result. On the other side there was a payment system integrated and an employee management panel.

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Responsibilities:
  • Integrated Payment using Stripe;
  • Wrote complex, responsive views with different levels of authentication access in NextJS & Tailwind.
Project Tech stack:
Next.js
Tailwind CSS
Stripe API
Node.js
MySQL
Nginx
Docker
Full-stack Developer
Aug 2021 - Nov 20212 months
Project Overview

Automating process between gathering forms and sending them to the print. Details sent to the email through forms are picked up by a bot that sniffs the email inbox, filters information from the form, and saves it in the NoSQL database. On the frontend there was an app written in NextJS and pdf creator, allowing to download dynamically created letters.

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Responsibilities:
  • Configured Firebase;
  • Communicated with NoSQL Database;
  • Created Python bot sniffer;
  • Created frontend with login;
  • Connected frontend to backend;
  • Dynamically created pdfs from data;
  • Dockerized the whole app so it can work with different emails.
Project Tech stack:
Python
Next.js
Firebase
Full-stack Developer
Mar 2020 - Sep 20205 months
Project Overview

Trading bot based on AI predictions. Scrapper was hosted on Heroku as a Python bot, which every few hours scrapped YahooFinance for price data. It is then appended to the file on AWS S3. Then the data was used to train the machine learning model and based on that we were making price predictions.

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Responsibilities:
  • Configured scrapper and hosted it on Heroku;
  • Created machine learning model with Tensorflow;
  • Created plots with Matplotlib;
  • Integrated python with Metatrader 5.
Project Tech stack:
Heroku
Python
AWS
Tensorflow

Education

2021
Computer Science
Bachelor

Languages

English
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