John Kapolos, Serverless Developer in Heraklion, Greece
John Kapolos

Serverless Developer in Heraklion, Greece

Member since September 9, 2015
John has been freelancing since the early 2000s. He has been working full-time remotely for US/UK companies as an all-around developer. He specializes in SPA development with React and Ember.js. On the back-end, he loves working with Node and PHP. In his spare time, he plays with DevOps and maintains his personal distributed infrastructure for fun.
John is now available for hire




Heraklion, Greece



Preferred Environment

Docker, Git, WebStorm, Windows Subsystem for Linux (WSL), Windows

The most amazing...

...thing I've coded was a fully featured major site from scratch finished on my own (Twitter-like following, Facebook-like feed, on-site mail, and much more).


  • Senior Full-Stack Developer

    2022 - 2022
    Toptal Project - Advanced Crypto Wallet
    • Created integrations with multiple blockchains, like Bitcoin, LTC, DOGE, Ethereum, Polygon, Solana, etc.
    • Implemented full crypto token support (ERC-20, BEP-20, ERC-721).
    • Implemented the exchange and currency integrations.
    Technologies: JavaScript, React, Web3.js, Ethers.js, Crypto, APIs
  • Senior Full-stack Developer

    2018 - 2022
    Legacy Research Group
    • Architected and developed the whole front-end React app from scratch to completely replace the previous technology (WordPress) for all the client's brands (highly modular and customizable for each brand).
    • Created APIs (Node.js, AWS Serverless) to help with the back-end development.
    • Built, maintained, and expanded the web app that powers a $200 million/year product fulfillment process across multiple brands.
    Technologies: React, AWS, Serverless, Node.js, TypeScript, PureScript, Redux
  • Back-end Developer (Node)

    2018 - 2018
    • Created a system to render arbitrary HTML to PDF.
    • Implemented rendering to PDF via HTML templates/partials and integrated everything with their data back-end.
    • Exported reports to Google Sheets via templates, integrating the reports with the team drive and back-end.
    Technologies: Rendering, PDF, Browser Automation, Linux, Google APIs, Node.js
  • Front-end Developer

    2018 - 2018
    • Implemented streaming USB camera to browser (local).
    • Implemented peer to peer video streaming via WebRTC (remote).
    • Implemented channels—users can stream their own camera and also view other channels.
    • Created the members' site.
    Technologies: WebRTC, React
  • Full-stack Developer (Node, React)

    2017 - 2017
    SBProject, LLC (via Toptal)
    • Implemented a customized S3 file sharing on Lamda using serverless.
    • Implemented the MVP for a calling-center SPA, using React (+MobX).
    • Implemented the MVP for lead-reporting.
    • Implemented deeply integrated authentication with AWS Cognito.
    Technologies: Serverless, React, Node.js
  • Freelance Front-end Developer

    2017 - 2017
    QPID Health (via Toptal)
    • Refactored the client's old Ember API to the newest and latest.
    • Implemented a series of new features on the front-end as the corresponding endpoints from the back-end became available.
    Technologies: Ember.js
  • Front-end Developer

    2017 - 2017
    Joinesty (via Toptal)
    • Reviewed the existing extension and created a plan for the Safari implementation without rewriting/forking the app.
    • Identified the Chrome extension API that had to be stubbed for Safari.
    • Create a compatibility layer between Chrome/Safari for the previously identified API subset to be used as a drop-in addition for the extension to run on Safari.
    Technologies: Safari, Chrome Extensions
  • Freelance Front-end Developer

    2016 - 2017
    Funding Gates (via Toptal)
    • Migrated an old hybrid Ember 1/Rails app to Ember 2 with proper API support.
    • Implemented new features that helped brings the company offer to the mid-size market, netting hundreds of thousands in new sales in the first few months.
    • Completely rewrote the test suite using the latest best practices.
    • Worked locally in the company's Manhattan office for ~40 days along with the rest of the team during the re-launch period.
    Technologies: Ember.js
  • Freelance Web Developer

    2016 - 2017 (via Toptal)
    • Tasked to make changes to the company's main site in order to add new functionality and a new design to part of it.
    • Converted from designer files to a WordPress theme.
    • Implemented user features in the WordPress back-end.
    • Implemented WordPress widgets.
    • Created responsive design with extra mobile optimizations as per the designer's schemata.
    • Retained for fixed/enhances after the bulk of the work completed.
    Technologies: CSS, JavaScript, PHP, WordPress
  • Freelance Ember.js Developer

    2016 - 2016 (via Toptal)
    • Handled the bulk of Ember development on a large project for one of the company's clients, totaling around forty non-trivial components, 250 "pages," and over 700 tests.
    • Contributed to key architectural decisions early in the project, responsible for taking it in the way in was implemented.
    Technologies: Ember.js
  • Freelance Full-stack Developer

    2016 - 2016
    Future Drone Cloud (via Toptal)
    • Created the back-end as an OwnCloud app via its respective framework (code + DB).
    • Created a JSON API service for the OwnCloud back-end to expose the functionality to the front-end.
    • Created the front-end SPA for the job submissions and general client functionality (in Ember.js).
    • Created the front-end SPA for the administrators/management and related functionality (in Ember.js).
    • Created the system for contract generation from the job submission data and manual entries.
    • Created the integrations with third-party systems such as RightSignature (document signing) and Google Maps.
    Technologies: MySQL, PHP, OwnCloud, JSON API, Ember.js
  • Freelance Front-end Developer

    2015 - 2015 (via Toptal)
    • Developed for the TED Ed analytics back-end as a drop-in extra programmer under TED's Sam Selikoff.
    • Fixed open issues (bugs and improvements).
    • Created the front-end of the demographics section of the analytics platform.
    • Created all the Ember components for the Demographics section.
    • Refactored previous code to make it generic enough for reuse over different sections of the platform.
    • Conducted unit tests and integration tests.
    Technologies: Git, CSS, Emacs, JavaScript, Ember.js
  • Full-stack Web Developer

    2014 - 2015
    • Architected the design of the system in all its details for efficiency and scalability.
    • Created the APIs (customer-facing, back-end-facing, and internal).
    • Created the customer-facing front-end.
    • Created the administrator back-end as an SPA (Single Page App) with Ember.js.
    • Created the mobile native application in Appcelerator.
    Technologies: Appcelerator, MySQL, ArangoDB, Ember.js, Node.js, PHP
  • Full-stack Developer

    2014 - 2015
    Crowdster (ex-Karma411)
    • Developed fully customized WordPress features.
    • Created front-end responsive designs.
    • Did AWS DevOps.
    • Integrated with legacy systems.
    • Created speed/SEO optimizations on the existing platforms.
    Technologies: Front-end, Node.js, PHP, WordPress
  • Full-stack Developer

    2012 - 2013
    • Merged their three different back-ends into one system.
    • Implemented the design and features of "version 2" of the site.
    • Did DevOps on various systems.
    • Created automation systems for backups/emails, etc.
    • Created data-based insights via statistical analysis.
    Technologies: Front-end, MySQL, PHP
  • Loan Officer

    2008 - 2011
    Cooperative Bank of Chania
    • Started as a teller, worked my way up to main teller and customer service and ultimately into loans.
    • Attended various off-time seminars in the sector.
    Technologies: Finance
  • Developer

    2002 - 2011
    • Created a desktop application that monitors users' installed applications and automatically upgrades them to the latest version on the background. Also created the required administration back-end in PHP.
    • Built an SEO checking tool that examines around 30 factors of a site and then gave it a rank along with explanations of what is great and what is lacking.
    • Developed an eCommerce website for a local company in Magento, syncing catalog data from their legacy database system.
    • Programmed a phone application for two-factor authentication.
    • Developed a system that processed gigabytes of structured data and allowed the user to query via a web page for drilled down information in near real-time (max ten seconds' response time).
    • Built various aggregation/integration systems based on third-party APIs (Amazon, Facebook, Twitter, etc).
    Technologies: Front-end, Appcelerator, .NET, ArangoDB, Ember.js, Node.js, PHP
  • Mathematics Instructor

    2007 - 2008
    Private and Public Schools
    • Taught basic algebra to middle school kids.
    • Taught calculus, geometry, and statistics to high school kids.
    • Taught advanced statistics, linear optimization, and graph theory to university students.
    Technologies: Optimization, Geometry, Algebra, Calculus, Graph Theory, Statistics


  • Pramda: Practical Functional Programming in PHP

    A library to make functional programming in PHP practical, effective, and easy to use. Features automatically curried functions and baked-in lazy evaluation with a ton of functions for easy and practical use. Fully tested, with a lot of documentation (and much more docs coming up soon).

  • React-Godfather

    React-Godfather aims to explore an alternative mental model for function components. It adds a thin layer between your shiny components and React, quietly instrumenting things behind the scenes - and it wants to make you an offer you can't refuse.

    Here is what you get:
    • A very natural, top-down local state management which does not feel like a DSL.
    • Plays great with your existing code - you can progressively adopt it in your code-bases.
    • Fully Asynchronous components to await all you want, even within the render function.
    • Supports Async generators, for all your yielding extravaganzas.
    Code-splitting without wrapping.
    • Wings for your junior team colleagues.

  • Linux Best Practices and Tips by Toptal Developers (Publication)
    This resource contains a collection of Linux best practices and Linux tips provided by our Toptal network members.
  • Toptal Mentor
    John is a mentor in the Toptal Global Mentor’s Program. This program is a partnership between Toptal and General Assembly to provide high quality mentorship for students from minority and low income backgrounds who are looking to begin their careers as professional software engineers. John shows commitment to diversity in tech by mentoring a General Assembly student every week for a year, covering everything from coding tips and tricks to advice on making it in the industry.


  • Languages

    CSS, PHP, HTML5, JavaScript, ECMAScript (ES6), SQL, Less, Haml, Visual Basic .NET (VB.NET), ES7, Sass, Bash Script, TypeScript, PureScript
  • Frameworks

    Express.js, Ember.js, Bootstrap 3, React Native, Redux, .NET, Next.js
  • Libraries/APIs

    React, Ember Data, jQuery, Node.js, MobX, JSON API, WebRTC, Google APIs, Google API, Amazon EC2 API, Twitter API, Facebook API, Amazon API, Web3.js
  • Tools

    PHP-FPM, Apache, NGINX, Stylus, Varnish, GitHub, Git, PhpStorm, Brunch, Gulp, Grunt, Sequelize, Vagrant, WebStorm, Appcelerator, Emacs, SaltStack, Ansible, MATLAB, Adobe Photoshop, Appcelerator Titanium
  • Paradigms

    Asynchronous Programming, Promise, Responsive, Responsive Web Design (RWD), Functional Programming, Object-oriented Programming (OOP), Microservices
  • Platforms

    Linux, Docker, WordPress, Safari, Windows, Amazon Linux, Azure
  • Other

    Ember CLI, Serverless, Ubuntu Server, GNU, Front-end, Finance, Statistics, Graph Theory, Calculus, Algebra, Geometry, Optimization, Chrome Extensions, Browser Automation, PDF, Rendering, AWS, Windows Subsystem for Linux (WSL), HAProxy, Ethers.js, Crypto, APIs, PWA
  • Storage

    Amazon S3 (AWS S3), NoSQL, Memcached, Redis, MySQL, ArangoDB, OwnCloud


  • Master of Liberal Arts in Software Engineering
    2018 - 2022
    Harvard Extension School - Cambridge
  • Master of Science Degree in Economic Theory and Policy
    2005 - 2007
    University of Crete - Crete
  • University Degree in Applied Mathematics
    2000 - 2004
    University of Crete - Crete

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