Crafted before AI


Full Stack Developer | JavaScript | React, Next.js, Node.js, SQL

$

Upwork
Top Rated freelancer
Client rating
5.0
Writing code
Since 2019
Novi Sad, Serbia
 
01Stack

Technology Mastery

In my journey as a developer, I've embraced a philosophy that shapes how I represent my skills: there's always room for growth, always something new to learn, always a way to improve. This reflects my belief that in technology, mastery is a continuous journey, not a final destination.

Growth & Innovation

I actively research emerging technologies, experiment with new frameworks, and explore better approaches to solve problems. Every project is an opportunity to innovate — whether it's optimizing performance, implementing cutting-edge features, or finding more elegant solutions.

Experience & Mastery

My proficiency levels are carefully calibrated based on my hands-on experience and the depth of my understanding. 'Advanced' doesn't mean perfect - it means I've built complex solutions and overcome significant challenges.

01Programming Languages

  • JavaScriptAdvanced
  • TypeScriptAdvanced
  • Java
  • Python
  • PHP

02Frontend Technologies

  • ReactAdvanced
  • Next.jsAdvanced
  • Tailwind CSS
  • Redux
  • SEO

03Backend & APIs

  • Node.jsAdvanced
  • AI Integration
  • NestJSIntermediate
  • DjangoIntermediate
  • LaravelIntermediate

04Databases

  • PostgreSQLAdvanced
  • MySQLAdvanced
  • SupabaseAdvanced
  • MongoDBIntermediate

05Mobile Development

  • React NativeAdvanced

06Tools & Platforms

  • CMS SystemsAdvanced
  • Git
  • Strapi
02Experience

Experience & Education

Professional Experience

  1. 2025 - Present

    Codeflex

    Full Stack Developer

    • Developing web applications with PHP, JavaScript, TypeScript, Next.js and Strapi CMS
    • Built internal tools used across the company
    • Built and maintained webshops

  2. 2025 - Present

    Upwork & direct clients

    Remote · Freelance

    Freelance Full Stack Developer

    • Top Rated on Upwork with a 5.0 rating on every review
    • Building and rescuing React, Next.js, Node.js and Supabase products — from multi-tenant analytics platforms to auth integrations and migrations
    • Working directly with clients from scoping to delivery

  3. June 2022 - December 2024

    EPAM Systems

    Novi Sad · Full-time

    Full Stack Developer

    • Developed complex enterprise applications using React.js and Next.js, implementing advanced state management patterns and performance optimizations
    • Built comprehensive testing strategies using Jest, ensuring code reliability and maintainability
    • Optimized database performance through efficient SQL query design and schema improvements
    • Contributed to system architecture decisions and technical strategy discussions
    • Collaborated with cross-functional teams to deliver scalable, high-quality solutions

  4. December 2020 - June 2022

    Vivify Ideas

    Novi Sad · Full-time

    Full Stack Developer

    • Built robust web applications using ReactJS, Redux, Node.js, Django, and C#
    • Developed and optimized SQL queries and database schemas for improved performance
    • Created responsive, user-friendly interfaces with modern HTML/CSS practices
    • Implemented comprehensive testing with Jest to ensure code quality and reliability

  5. April 2019 - May 2020

    OCTA IT Sourcing

    Novi Sad · Internship

    Scholarship Student

    • Developed web applications using Angular 2+, Node.js, HTML/CSS, Git, and NoSQL databases

Education

  1. 2016 - 2020

    Faculty of Technical Sciences, University of Novi Sad

    Novi Sad · Bachelor's

    Bachelor's degree, Computer Software Engineering

    • Studied programming languages including Java, C#, and JavaScript, with frameworks such as React, Angular, Node.js, and .NET
    • Developed expertise in SQL database management and optimization
    • Built strong foundation in Object-Oriented Programming (OOP) and RESTful API design
03Work

Professional Projects

Recent client work from Upwork and freelance engagements, plus the products I helped build at EPAM, Vivify Ideas and OCTA.

Upwork client/Apr – Jun 2026

Ad Analytics Platform

Full Stack Developer

Internal multi-tenant analytics platform: 46 analysis modules on top of the Windsor.ai API, Supabase auth with role-based access, a Claude-powered commentary engine and a full React dashboard.

  • React
  • Node.js
  • Supabase
  • PostgreSQL
  • Windsor.ai API
  • Claude API
Read the review
analysis modules
0
analysis modules
RLS policies
0
RLS policies
database tables
0
database tables

Proposed beyond the brief: analysis caching, AI rules with global / module / client granularity, and progressive loading.

04Reviews

What clients say

Every review on my Upwork profile so far is five stars. Here is what clients wrote, word for word.

5.0

“He didn’t just execute the spec — he improved it.”

Mateja is one of the best developers I’ve worked with. We hired him for a complex internal analytics platform — 46 analysis modules, Windsor.ai API integration, Supabase auth with multi-tenant RBAC, Claude AI commentary engine, and a full React dashboard. He didn’t just execute the spec — he improved it.

Upwork client · project

Deploy & Integrate Pre-Built Ad Analytics Dashboard (React + Node.js + Supabase)

5.0

“He said it would take 3-4 days and got it done in 2 days!”

Mateja was incredible to work with on this project of creating a SaaS system. I had no clue how any of it worked and he was great to talk with and explain what he needed to get the job done. I will definitely be working with Mateja in the future for updates on this system and for other creations. He said it would take 3-4 days and got it done in 2 days! Thank you!

Upwork client · project

React Developer Needed — Add Supabase Auth & User Accounts to Existing App

  • Reliable
  • Collaborative
  • Clear Communicator
  • Accountable for Outcomes
  • Detail Oriented
5.0

“Excellent work – fast, precise, and highly skilled”

Mateja solved a very tricky Chrome authentication lock issue in under one hour, after it had caused serious problems for a long time. He immediately understood the root cause, worked in a structured way, and delivered a clean and robust solution.

Upwork client · project

Fixing bug in a very simple Nuxt - Supabase App

  • Committed to Quality
  • Solution Oriented
  • Clear Communicator
5.0

“The work is always better than expected.”

Mateja is an outstanding developer. Fast, clear in communication and delivers exactly what you need without any fuss. The work is always better than expected. I highly recommend him.

Upwork client · project

Migrating blog to Vercel: database, storage and repo transfer

  • Committed to Quality
  • Clear Communicator
  • Detail Oriented
05Projects

Personal Projects

Real-world applications demonstrating full-stack development, AI integration, and production deployment experience.

  • 01
    Live on AndroidiOS soon
    Kalori website: Track your nutrition effortlessly

    Kalori

    Calorie and macro tracker with AI food logging by text or voice, a 4M+ item food library, weight tracking with progress photos and timeframe-based calorie planning.

    • React Native
    • Expo
    • Node.js
    • Supabase
    • OpenAI API
    Visit website
  • 02
    Live
    Hero section of this portfolio

    Professional Web Portfolio

    The site you’re on. Built for speed and SEO, responsive down to small phones, with motion used where it helps.

    • Next.js
    • TypeScript
    • Tailwind CSS
    • Framer Motion
    • Vercel
    You are here

  • More to come

06Process

My Development Approach

I believe great web development is about more than just writing code. It's about continuous learning, embracing new technologies, and finding innovative solutions to create exceptional digital experiences. Every project is an opportunity to explore cutting-edge technologies and deliver solutions that stand out.

  1. 01

    Project Discovery

    Every project starts with understanding your unique needs and vision. I take time to research your industry, analyze requirements, and identify the best technological approaches that will give your project a competitive edge.

  2. 02

    Innovation & Research

    I believe each project is an opportunity to innovate. I actively research and evaluate emerging technologies and development trends that could enhance your project, ensuring you get the most modern and efficient solutions.

  3. 03

    Agile Development

    Using an iterative development approach, I deliver value continuously. This allows for quick adjustments based on your feedback, ensuring the final product perfectly matches your vision while maintaining high code quality.

  4. 04

    Clear Communication

    I maintain transparent and proactive communication throughout the project. You'll receive regular updates on progress, quick responses to your questions, and clear explanations of technical concepts in understandable terms.

  5. 05

    Continuous Growth

    I approach each project as an opportunity to push boundaries. Whether it's exploring new frameworks, implementing cutting-edge features, or optimizing performance, I'm committed to delivering solutions that exceed expectations.

  6. 06

    User-Centric Development

    Every development decision is made with the end-user in mind. I focus on creating intuitive interfaces, smooth user flows, and accessible designs that ensure your users have the best possible experience across all devices.

07Contact

Let's Build Your Next Project

As a fullstack developer, I specialize in creating exceptional web experiences. I'm ready to help turn your vision into reality with modern, responsive, and user-friendly solutions.

Ready to Start?

Whether you have a specific project in mind or need consultation on your web development needs, I'm here to help. Let's discuss how we can work together to achieve your goals.

Prefer to hear it from me?Intro video
Email[email protected]Phone+381 69 4554024
LocationNovi Sad, Serbia (CET/UTC+1)
0/40 min