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Zsolt Bako
Verified Expert in Engineering
Full-stack Developer
Weston-super-Mare, United Kingdom
Toptal member since December 4, 2015
Bio
Zsolt is a self-taught developer and entrepreneur, a born problem-solver who started coding at age eight. With 12 years of full-stack experience rooted in the JavaScript ecosystem, he co-founded a social network startup and has led remote teams on greenfield projects. Over the past two years, he has shipped multiple AI-powered products using Claude Code as his daily driver, spanning voice interfaces, conversational AI, and SaaS with LLM-driven features. Zsolt delivers exceptional results fast.
Portfolio
Scope Tickets
Next.js, JavaScript, Front-end Development, Front-end Design, Figma, Stripe...
The Think Tank Education LLC
React, Node.js, JavaScript, NestJS, MobX, Redis, MongoDB, Scaling, Optimization...
Elemental Prep, LLC
Amazon Web Services (AWS), Audits, Technical Leadership, Full-stack Development...
Experience
- JavaScript - 20 years
- React - 12 years
- Node.js - 12 years
- Full-stack - 12 years
- TypeScript - 11 years
- Architecture - 9 years
- Claude Code - 1 year
- AI Architecture - 1 year
Preferred Environment
Docker, Git, Visual Studio Code (VS Code), Linux, Claude Code
The most amazing...
...thing I've built is a voice AI assistant that lets children turn their ideas into playable game mods just by talking.
Work Experience
Senior Front-end Developer
2022 - 2026
Scope Tickets
- Took over the front-end development of an event ticketing system for university events.
- Refactored parts of the business logic to match the back end closely and eliminate bugs.
- Improved the integration with Stripe Payment Elements and an internal ticket escrow system.
- Enhanced the themed UI to be consistent with the design.
- Made changes to the design of the UI components to improve readability and achieve a sleek and modern user interface.
- Implemented ticketing for event series, timed tickets, and multi-day tickets.
Technologies: Next.js, JavaScript, Front-end Development, Front-end Design, Figma, Stripe, Webpack, Redux, React, C#, C#.NET, React Query, Lodash, Agile Software Development, CI/CD Pipelines, Sentry
Node.js and React Developer
2022 - 2026
The Think Tank Education LLC
- Planned, architected, and developed an educational app where students can solve math quizzes and see a detailed report of their progress during the year. It allows their teachers and school admins to see aggregated and individual statistics.
- Coordinated with the client to determine and fine-tune the requirements for a great user experience.
- Architected a full-stack web application from scratch, balancing the ability of rapid prototype development and future scalability.
- Coordinated the production launch of the application, measured various performance metrics, ran customized benchmarks to estimate the solution's scalability, and continuously improved the app to allow the smooth calculation of millions of results.
- Created a data pipeline for continuously calculating dozens of aggregated analytics based on individual student results to provide excellent visibility for teachers, school administrators, and internal monitoring.
- Designed the app's UI in line with the requirements of the clients and different kinds of users. Created reusable front-end components to achieve the desired goals and make a great user experience.
- Integrated a LaTeX presentational component to display math quiz problems and answers to accurately and beautifully present scientific and math formulas.
- Created a dynamic quiz generator that opens up the possibility of customized learning experiences.
Technologies: React, Node.js, JavaScript, NestJS, MobX, Redis, MongoDB, Scaling, Optimization, Architecture, Full-stack, Tailwind CSS, Responsive UI, Front-end, Chart.js, LaTeX, Design, Software Architecture, Software Engineering, E2E Testing, Playwright, Data Visualization, Webpack, Redux Toolkit, API Integration, Unit Testing, Scalability, CircleCI, Bash Script, Moment.js, Lodash, NoSQL, Agile Software Development, Front-end Architecture, CI/CD Pipelines, Sentry, Large Language Models (LLMs)
Lead Full-stack Developer
2025 - 2025
Elemental Prep, LLC
- Architected a complete greenfield full-stack application on Next.js and Supabase, replacing a legacy Bubble prototype with a scalable, production-grade codebase.
- Designed and implemented a complex data model for a graph-like learning structure encompassing video content, mental workouts, and granular user progress tracking.
- Established Claude Code as the team's primary development tool, defining workflows and patterns that accelerated feature delivery across the full stack.
- Led and coordinated a growing development team, translating evolving business requirements into clear technical specifications and ensuring consistent implementation across contributors.
- Built the authentication system using Supabase Auth with Google and Apple SSO plus magic link email login.
Technologies: Amazon Web Services (AWS), Audits, Technical Leadership, Full-stack Development, Auditing, Technical Support, IT Audits, Google Cloud Platform (GCP), Node.js, TypeScript, React, Next.js, Supabase, Supabase Auth, PostgreSQL, Claude, Claude Code, Prompt Engineering
AWS/Node.js Full-stack Developer
2025 - 2025
Bryght Labs Inc
- Developed a comprehensive game analyzer that processed thousands of incomplete chess matches, revealing critical insights into match abandonment and technical issue patterns, enabling leadership to make data-driven decisions.
- Re-architected and reimplemented the internal admin application using Refine, halving the dashboard maintenance complexity and streamlining the process of adding new performance metrics, significantly improving operational efficiency.
- Initiated strategic infrastructure planning for backend scalability, developing a roadmap for auto-scaling, enhanced monitoring tools, and standardized API specifications to prepare the platform for seasonal traffic peaks and future growth.
Technologies: Node.js, Amazon Web Services (AWS), Puppeteer, PostgreSQL, Socket.IO, React, Amazon EC2, TypeScript, Prisma
Senior Front-end Developer
2024 - 2024
Stubhub - Engineering
- Strengthened the team with rapid development at a critical phase to achieve a timely and high quality MVP release.
- Rewrote the Column Formula Builder using a custom-built tokenized formula editor to provide a flexible tool with great UX for users.
- Set up E2E tests using Playwright to improve the app's reliability and discover bugs before releases.
- Developed new features and improvements and fixed bugs in the client's PoS app following the stakeholders' quickly changing requirements.
Technologies: React, TypeScript, JavaScript, Front-end, React Query, C#, C#.NET, Vanilla Extract CSS, Playwright, E2E Testing, Unit Testing, Lodash, Agile Software Development, Radix UI, Agile
Back-end Team Lead & Architect
2022 - 2023
Fabzen Technologies
- Led a continuously growing back-end development team of a real-money gaming company.
- Crafted the microservices architecture of a multi-game single platform back end that serves millions of players.
- Designed and created a vastly scalable event bus built on top of Amazon SQS, which had AMQP and Kafka-like capabilities with a more straightforward interface and lower maintenance needs.
- Translated the continuously changing business requirements into actionable development stories.
- Developed a scheduler-based real-time gaming engine suitable for card games and board games using Socket.IO.
- Coordinated the integration with the mobile app by discussing and specifying the internal REST APIs and Socket.IO interface.
Technologies: Node.js, Gaming, Socket.IO, RabbitMQ, Microservices, Concurrent Programming, TypeScript, Amazon Simple Queue Service (SQS), Amazon Web Services (AWS), Amazon S3 (AWS S3), Amazon Elastic Container Service (ECS), Docker, NestJS, Jest, Message Bus, Real-time Data, Message Queues, AsyncAPI, OpenAPI, Software Architecture, Back-end, REST APIs, Software Engineering, Team Management, Team Mentoring, Technical Hiring, Cross-functional Collaboration, Jira, Scrum, Amazon ElastiCache, Amazon Cognito, Technical Leadership, JavaScript, API Integration, Scalability, CircleCI, Lodash, Architecture, Amazon EC2, Agile Software Development, WebSockets, Sentry, Event-driven Architecture
Senior Full-stack Developer
2022 - 2022
Fly & Fetch
- Contributed to the rewrite of the Svelte-based front end.
- Implemented new features across the full stack.
- Stabilized the platform by rewriting error-prone parts of the codebase and adding an automated end-to-end testing suite using Playwright.
- Fixed security vulnerabilities to ensure the platform's integrity and data safety.
- Improved the developer experience and efficiency in the team by switching to better tooling and services.
Technologies: JavaScript, FeathersJS, MongoDB, MongoDB Atlas, Svelte, Amazon S3 (AWS S3), APIs, REST, Stripe API, Stripe, Web Development, CSS, Amazon Web Services (AWS), REST APIs, GitHub, HTML, Full-stack, Full-stack Development, Responsive UI, Tailwind CSS, E2E Testing, Node.js, CircleCI, Moment.js, Lodash, Architecture, Facebook API, Amazon EC2, NoSQL, Agile Software Development
Senior Full-stack Developer
2020 - 2022
Argo Group
- Reimplemented an internal document store and a search platform from scratch as a sole developer.
- Architected and built a Node.js back end using Elasticsearch as a central document metadata storage and search engine.
- Created a React-based front end that provided an instant search functionality to the users.
- Implemented complex filtering, verification, and exporting capabilities.
- Maintained various other legacy applications.
Technologies: AWS Lambda, Amazon S3 (AWS S3), Amazon API Gateway, AWS IAM, Node.js, Express.js, React, Elasticsearch, Web Development, CSS, SQL, Amazon Web Services (AWS), REST APIs, GitHub, Amazon RDS, PostgreSQL, HTML, Full-stack, MySQL, Full-stack Development, Responsive UI, Concurrent Programming, Serverless Architecture, Lambda Functions, Amazon Cognito User Pools, Amazon Cognito, Okta, JavaScript, API Integration, Serverless, Lodash, Agile Software Development
Senior Front-end Engineer
2018 - 2020
Patron Technology
- Developed a powerful event marketing analytics platform as part of a small team.
- Focused primarily on implementing new features on the front end, such as advanced filtering, visualization components, and user management.
- Extended the internal API back end to provide the necessary data efficiently from the Elasticsearch data warehouse and MySQL.
- Implemented React components using D3.js to visualize data on the analytics dashboard.
- Created and improved reusable visualization components using Storybook.
Technologies: Elasticsearch, MySQL, Node.js, D3.js, Redux, TypeScript, React, Web Development, CSS, SQL, Amazon Web Services (AWS), REST APIs, GitHub, Amazon RDS, PostgreSQL, HTML, Dashboards, Data Analytics, Responsive UI, Storybook, Data Visualization, Webpack, JavaScript, Lodash, Agile Software Development, Agile
Senior Full-stack Developer
2016 - 2018
StartMonday
- Led the building of a Kanban-like applicant tracking system using TypeScript, React, MobX, and Firebase.
- Rebuilt the legacy web app for job seekers using TypeScript, React, MobX, and Video.js. Applicants could record videos using the app.
- Contributed to the core rewrite to handle different user journeys well using the state machine approach.
Technologies: MongoDB, GraphQL, Firebase, MobX, React, TypeScript, AWS Lambda, Node.js, Express.js, Web Development, CSS, Amazon Web Services (AWS), REST APIs, GitHub, HTML, Full-stack, Full-stack Development, Responsive UI, JavaScript, API Integration, CircleCI, Amazon EC2, Agile Software Development, Agile, CI/CD Pipelines
Back-end Developer
2015 - 2016
Statzup
- Developed a scheduled digester that processes third-party data to an in-house database.
- Extended the REST API of the game.
- Refactored legacy codes into maintainable software.
- Developed new functionalities for the existing back end.
- Integrated PayPal payment solutions.
Technologies: Kue, MongoDB, Express.js, Node.js, Web Development, REST APIs, Gaming, JavaScript
Lead Developer and Co-founder
2013 - 2015
Miutcank.hu
- Prototyped the MVP rapidly using Meteor.
- Architected the final product with the help of a senior adviser.
- Developed microservices for a social network.
- Planned and implemented RabbitMQ-based communication between microservices.
- Created a custom algorithm to determine a neighborhood of users.
- Set up a scalable infrastructure for the growing social network.
- Led a small team of talented developers.
Technologies: React, Redis, RabbitMQ, Restify, Express.js, Node.js, Web Development, CSS, REST APIs, Hapi.js, HTML, Full-stack, Full-stack Development, Azure, Sockets, Responsive UI, Socket.IO, Concurrent Programming, JavaScript, API Integration, AMQP, Architecture, Facebook API, CoffeeScript, Google API, NoSQL, Agile Software Development
Experience
Blocky
An AI-powered voice assistant that lets children create playable game modifications for Luanti (an open-source voxel game engine similar to Minecraft) using only their voice.
The app runs on Android and listens for a wake word, then captures the child's idea via speech-to-text. The transcript is sent to a FastAPI backend orchestrating two isolated Claude Code instances in Docker containers: a Talker instance that converses with the child to understand and refine their idea, and a Builder instance that generates the actual Luanti mod code.
While the Builder works, the Talker provides real-time progress updates via text-to-speech on the mobile app. Once the mod is ready, the server restarts the Luanti instance and the child can immediately play their creation.
Designed the full system architecture, built the FastAPI orchestration layer, developed the React Native Expo mobile client, and engineered the prompt workflows for both AI agents.
The app runs on Android and listens for a wake word, then captures the child's idea via speech-to-text. The transcript is sent to a FastAPI backend orchestrating two isolated Claude Code instances in Docker containers: a Talker instance that converses with the child to understand and refine their idea, and a Builder instance that generates the actual Luanti mod code.
While the Builder works, the Talker provides real-time progress updates via text-to-speech on the mobile app. Once the mod is ready, the server restarts the Luanti instance and the child can immediately play their creation.
Designed the full system architecture, built the FastAPI orchestration layer, developed the React Native Expo mobile client, and engineered the prompt workflows for both AI agents.
KitcheNext
A meal planning, recipe collection, and shopping list optimization SaaS web application. Users collect recipes from the central database via URL scraping or OCR import of recipe card photos, then receive AI-powered meal suggestions based on learned dietary preferences, budget constraints, and leftover ingredients to minimize waste.
The app generates optimized weekly shopping lists by aggregating and deduplicating ingredients across planned recipes.
Built the Next.js front end with a mobile-first responsive design, Supabase backend for database and authentication, a FastAPI service for AI-powered meal recommendations using Claude, a separate FastAPI service for recipe card OCR, and an Express-based scraper for web imports. Architected the full system as a set of focused microservices and engineered the prompt workflows for preference learning and meal suggestion.
The app generates optimized weekly shopping lists by aggregating and deduplicating ingredients across planned recipes.
Built the Next.js front end with a mobile-first responsive design, Supabase backend for database and authentication, a FastAPI service for AI-powered meal recommendations using Claude, a separate FastAPI service for recipe card OCR, and an Express-based scraper for web imports. Architected the full system as a set of focused microservices and engineered the prompt workflows for preference learning and meal suggestion.
bLocal
http://blocal.coAs a lead developer, I mainly contributed to the back end of the application, and I also developed some parts of the front end. The Node.js back end is based on a microservices architecture and provides advanced solutions for calculating a dynamic neighborhood boundary for users, generating relevant news feed, showing targeted advertisements, and more.
Education
2005 - 2008
Professional Degree in Software Designer Mathematics
Eötvös Loránd University - Budapest
Skills
Libraries/APIs
React, Node.js, MobX, REST APIs, D3.js, Lodash, Moment.js, Restify, AMQP, Stripe, Sockets, Socket.IO, Chart.js, React Query, Claude API, Google API, PayPal API, Facebook API, Stripe API, OpenAPI, Playwright, Vanilla Extract CSS, Puppeteer
Tools
GitHub, Claude, Claude Code, Gulp, Jira, Bamboo, Git, RabbitMQ, Kue, CircleCI, Redux Toolkit, Sentry, Expo, Babel, Docker Swarm, AWS IAM, MongoDB Atlas, Figma, LaTeX, Amazon Simple Queue Service (SQS), Amazon Elastic Container Service (ECS), Amazon ElastiCache, Amazon Cognito, Webpack, Prisma, Whisper
Languages
TypeScript, JavaScript, CSS, HTML, PHP, SQL, Bash Script, Dart, Python, GraphQL, CoffeeScript, C#, C#.NET
Frameworks
Express.js, Koa, Redux, Flutter, Tailwind CSS, Hapi.js, Angular, FeathersJS, Svelte, AngularJS, NestJS, Next.js, Jest, React Native
Paradigms
Promise, REST, Agile Software Development, Microservices, Unit Testing, Concurrent Programming, E2E Testing, Serverless Architecture, Agile, Functional Reactive Programming, Scrum, Event-driven Architecture
Platforms
Linux, Docker, Heroku, Amazon Web Services (AWS), Amazon EC2, AWS Lambda, Google Cloud Platform (GCP), Firebase, MacOS, Azure
Storage
MongoDB, Amazon S3 (AWS S3), PostgreSQL, Redis, NoSQL, MySQL, Elasticsearch
Other
APIs, Full-stack, Web Development, Full-stack Development, Responsive UI, Front-end, Software Architecture, Back-end, API Integration, Prompt Engineering, Scalability, Caching, Cloud, Architecture, Amazon RDS, Dashboards, Data Analytics, Optimization, Data Visualization, Serverless, Lambda Functions, Front-end Architecture, WebSockets, CI/CD Pipelines, Large Language Models (LLMs), Supabase, Supabase Auth, AI Architecture, Chrome Extensions, Web Components, Amazon API Gateway, Gaming, Scaling, Storybook, Front-end Development, Front-end Design, Design, Software Engineering, Message Bus, Real-time Data, Message Queues, AsyncAPI, Team Management, Team Mentoring, Technical Hiring, Cross-functional Collaboration, Bluebird, Amazon Cognito User Pools, Okta, Technical Leadership, Radix UI, Audits, Auditing, Technical Support, IT Audits, FastAPI, Text-to-Speech (TTS), Optical Character Recognition (OCR)
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