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Andrej Gajdos, Web Development Developer in London, United Kingdom
Andrej Gajdos

Web Development Developer in London, United Kingdom

Member since March 14, 2016
Andrej is a technology consultant, software engineer, and tech blogger with over six years of experience delivering software. He has worked for clients all around the world in many different industries. A background in computer science and his ability as a full-stack developer allow him to create everything from small business websites to custom web applications. He makes complex problems simple with fast, clean, and maintainable code.
Andrej is now available for hire


  • Nash
    JavaScript, React, Gatsby, GraphQL, Styled-components, TypeScript
  • FastSwims
    JavaScript, React, Redux-Saga
  • Glofox
    React Native, Redux


  • JavaScript, 6 years
  • Web Development, 6 years
  • Single-page Applications (SPA), 3 years
  • React, 3 years
  • Koa, 1 year
  • Node.js, 1 year
  • PostgreSQL, 1 year
  • Redux, 1 year
London, United Kingdom



Preferred Environment


The most amazing...

...thing I've designed and developed is a portlet to build and visualize a social network as a directed multigraph.


  • React Developer

    2018 - 2019
    • Built the company's fully responsive website.
    • Built customizable UI components used across multiple projects.
    • Built functional prototypes of fund management and payment systems in the exchange platform.
    Technologies: JavaScript, React, Gatsby, GraphQL, Styled-components, TypeScript
  • React Developer

    2018 - 2018
    • Designed and built a functional prototype of event management platform for managing swimming teams and swimming competitions.
    • Designed a new user interface based on customer’s prototypes.
    • Built a functional prototype from scratch as a single page application.
    Technologies: JavaScript, React, Redux-Saga
  • React Developer

    2018 - 2018
    • Helped deliver a React Native project used for managing fitness studios.
    • Fixed various bugs and issues in the project.
    • Optimized the project for the Android platform.
    Technologies: React Native, Redux
  • Principal Software Engineer

    2017 - 2018
    • Designed and built an interactive podcast platform. Podcasters can upload audio files and add "spots" to specific moments in their podcasts, which can be anything from links, to social media posts, to other videos or images. Listeners are engaged with content, such as social media posts or preview of external web pages.
    • Built a single-page app from scratch with a complex user interface, including user interactions and animations.
    • Designed and developed a RESTful API server.
    Technologies: Heroku, Amazon S3, PostgreSQL, JavaScript, Node.js, Koa, Objection.js, Knex.js, React.js, Redux, D3.js, SVG, Webpack, Babel, Twitter API, InVision
  • Pre-sales Engineer

    2016 - 2017
    • Presented and demonstrated products to potential customers from all over the world.
    • Demonstrated product features to developer teams and showed how to use them in the development process with a specific workflow, environment, and toolset.
    • Helped sales associates close deals by presenting our products in specific use-cases.
    • Trained sales associates in how to effectively present and sell our tools to developer teams and managers.
    • Assisted customers with installation, troubleshooting, and other customer service for configuration issues.
    Technologies: Java
  • Software Engineer

    2015 - 2016
    • Implemented new features and fixed bugs in enterprise applications used for data quality management and rewrote UI components to use modern technologies.
    • Designed and implemented the front-end of an interactive application for customer data management.
    • Designed and implemented server-to-sever communication and server pushes in a GWT application.
    Technologies: Java, JavaScript, ES6, React.js, Flux, Immutable.js, Backbone.js, jQuery, Bootstrap, SCSS, Webpack, Gulp, Babel, D3.js, JSP, JSTL, JMS, ActiveMQ, Errai
  • Java Developer

    2013 - 2015
    Techniserv, Taranzo
    • Analyzed, designed, and implemented solutions for gathering and processing structured and unstructured data from social networks and various other sources.
    • Designed and implemented a module for building and visualizing a social network.
    Technologies: Java, JavaScript, Liferay, Spring MVC, Maven, JSP, JSTL, jQuery, Bootstrap, D3.js, Jung, OrietDB, YouTube and Twitter APIs
  • Software Tester

    2012 - 2013
    Amberg Group
    • Executed both manual and automated tests and analyzed the results.
    • Developed and maintained the whole test infrastructure with automated tests.
    • Designed test cases, wrote documentation, and reported issues.
    Technologies: JavaScript, Python, Ruby


  • Nash (Development)

    Blazing fast static website built with React and Gatsby. All pages are fully responsive and optimized for mobile viewing.

    Development tools: JavaScript, React, Gatsby, Styled-components, TypeScript

  • FastSwims (Development)

    Event management platform for managing swimming teams and swimming competitions. I designed a new user interface based on customer’s prototypes and built a functional prototype.

    Development tools: JavaScript, React, Redux-Saga

  • Saycaster (Development)

    An interactive podcast platform:

    - Podcasters upload their audio and add 5-20 spots to their podcasts
    - These spots can be anything from links, to social media posts, to other videos or images
    - Listeners can listen and comment on these specific spots

    Development tools: JavaScript, Node.js, Koa.js, PostgreSQL, Heroku, React, Redux, D3.js

  • Neo Transfer (Development)

    Neo-transfer allows you to log in with a private key, see balance, and transfer NEO or GAS within TestNet. The project is based on JS SDK for NEO blockchain.

    Development tools: Neon.js, React.js, Redux, Redux-Saga, Twitter Bootstrap

  • Newsfeed Cryptogoods (Development)

    A newsfeed for events on cryptogoods with a single, responsive page.

    Development tools: JavaScript, React.js, Redux, Redux-Saga, Twitter Bootstrap

  • Authenticating Users in SPA using Node, Passport, React and Redux (Development)

    User authentication in a single page application with Node, React, Redux and Koa combined with Passport.

    Development tools: JavaScript, Node.js, React, Redux, Passport.js

  • Nested Datatables (Development)

    jQuery DataTables plugin for rendering nested data tables in rows. Inner tables are independent of the data and layout from the outer table.

    Development tools: JavaScript, jQuery

  • Webpack Setup for ES6, React, Sass, and Bootstrap (Other amazing things)

    Webpack configuration to bundle ES6, React, Sass, and Bootstrap for production and development.

    Development tools: JavaScript, React, Webpack

  • Social Graph (Development)

    A Liferay portlet to visualize a social network as a directed multigraph. Jung library is used for building the multigraph, which is stored in OrientDB. Visualization and other components are built in D3.js and Bootstrap.

    Development tools: Java, JavaScript, Liferay, JSP, Jung, OrientDB, D3.js, Bootstrap

  • SVG Sprite into PNG (Development)

    A workflow converts SVG sprite into PNG images utilizing Gulp.

    Development tools: JavaScript, Gulp

  • Server Push in GWT Application with Errai (Development)

    Implementation of server push messages from server to client in GWT application with Errai framework.

    Development tools: Java, GWT, Errai

  • Contract Generator Tool (Development)

    Some insurance brokers have a list of insurances and clients in XLS format and need to generate various contracts based on a contract template in DOC and DOCx format. The user can set up a database (XLS or XLSx) and required columns, which will be parsed into the contract. The application has a database of insurance in SQLite. The main window contains a list of clients with detailed information, where the user can instantly search clients, add required information (date, overpayment, insurance from database), choose contract templates, and generate a contract (DOC or DOCx) for the client. The UI is built in WPF and ADO.NET is used for parsing data from a Microsoft Excel file.

    Development tools: C#/.NET, WPF, SQLite, ADO.NET

  • Personal Calendar (Development)

    A basic personal calendar application with two view modes (week/month). The application generates log files and uses a MySQL database. The presentation layer is built in Swing and SwingWorker. Connections to the database are developed in JDBC. The project contains simple JSP pages for viewing a list of events and their detailed information.

    Development tools: Java, JSP, Swing, SwingWorker, MySQL, JDBC

  • Guide to Data Synchronization in Microsoft SQL Server (Publication)
    Sharing related information among isolated systems has become increasingly important. There are many methods to choose from to perform that task for SQL Server, but it’s important to know which is better for each use case.
  • A Guide to Managing Webpack Dependencies (Publication)
    The Webpack module bundler processes JavaScript code and all static assets, such as stylesheets, images, and fonts. However, configuring Webpack and its dependencies can be cumbersome and not always a straightforward process, especially for beginners. In this article, Toptal Software Engineer Andrej Gajdos provides a guide with examples on how to configure Webpack for different scenarios and points out the most common pitfalls connected to project dependencies and their bundling when using Webpack.


  • Languages

    JavaScript, JavaScript 6, Object-oriented JavaScript (OOJS), HTML/CSS, CSS, HTML, CSS3, Java, HTML5, Less, SCSS, Sass, ECMAScript (ES6), SQL, C, Python, Ruby, PHP, C#, UML, C++, TypeScript, GraphQL
  • Libraries/APIs

    Underscore.js, Passport.js, jQuery Plugins, jQuery UI, Redux-saga, D3.js, React, Node.js, Immutable.js, JSTL, Chai, jQuery, Styled-components, GatsbyJS, JDBC, Backbone.js, OpenGL, Win32 API, WinForms, JMS
  • Paradigms

    Model View Controller (MVC), Object-relational Mapping (ORM), Agile Software Development, Functional Programming, REST, Object-oriented Programming (OOP), Object-oriented Design (OOD), Software Testing, Automated Testing
  • Storage

    JSON, PostgreSQL, Graph Databases, SQLite, MySQL, OrientDB
  • Other

    UI Development, Ajax, Front-end, Back-end Development, Single-page Applications (SPA), Writing, Presentations, Sales, Customer Service, Consultation, Web Development, Programming, Software Design, ESLint, Technical Consulting, Web Scraping, Data Visualization, Social Networks Development, Data Analysis, Liferay, BPM, Messaging Patterns, Windows Presentation Foundation (WPF), Sales Presentations
  • Frameworks

    Koa, Redux, Bootstrap, Spring MVC, Flux, JUnit, React Native, Ruby on Rails (RoR), JavaServer Pages (JSP), Swing, .NET
  • Tools

    Redux Thunk, Webpack, Gulp.js, Bower, Mocha, Gatsby, PostCSS, Knex.js, Babel, GitLab, GitHub Pages, GitHub, Trello, InVision, ActiveMQ, Maven
  • Platforms

    Firebase, Java EE, WordPress, Heroku, Amazon, MacOS, Windows, Linux


  • Master's degree in Service Science, Management, and Engineering
    2013 - 2015
    Masaryk University Brno - Brno
  • Erasmus exchange student in Master in Innovation and Research in Informatics
    2014 - 2014
    Polytechnic University of Catalonia - Barcelona
  • Bachelor's degree in Applied Informatics
    2009 - 2013
    Masaryk University - Brno
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