John is available for hire

John Kapolos

Verified Expert in Engineering

Full-stack Developer

Location

Heraklion, Greece

Toptal 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.js and PHP. In his spare time, he plays with DevOps and maintains his personal distributed infrastructure for fun.

Portfolio

Toptal Project - Advanced Crypto Wallet

JavaScript, React, Web3.js, Ethers.js, Crypto, APIs, Blockchain, HTML, CSS...

Legacy Research Group

React, Serverless, Node.js, TypeScript, PureScript, Redux, HTML, CSS...

SPARK!

Rendering, PDF, Browser Automation, Linux, Google APIs, Node.js, HTML, CSS...

Experience

PHP - 16 years JavaScript - 16 years Node.js - 8 years React - 7 years TypeScript - 6 years Functional Programming - 5 years Serverless - 5 years Ember.js - 5 years

Availability

Full-time

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).

Work Experience

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 exchange and currency integrations.

Technologies: JavaScript, React, Web3.js, Ethers.js, Crypto, APIs, Blockchain, HTML, CSS, Front-end, HTML5, TypeScript, REST APIs, GraphQL, Apollo, Jest, Responsive UI, Full-stack, Electron, Amazon Web Services (AWS), Cryptocurrency Wallets, Full-stack Development, Third-party APIs, Responsive Design, UI Components, API/Services Architecture, API Design, ESLint, CI/CD Pipelines, API Integration, Test Automation, Web3, UI Libraries, GitHub, Figma, Single-page Applications (SPA)

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, Serverless, Node.js, TypeScript, PureScript, Redux, HTML, CSS, JavaScript, Front-end, HTML5, Blockchain, REST APIs, GraphQL, Apollo, Jest, Responsive UI, Full-stack, PostgreSQL, Amazon Web Services (AWS), Payment APIs, Admin Panels, Analytics, Full-stack Development, Third-party APIs, Responsive Design, MongoDB, Next.js, UI Components, Amazon Cognito, Tailwind CSS, Express.js, Microservices, Redis, API/Services Architecture, API Design, ESLint, Kubernetes, CI/CD Pipelines, Sentry, API Integration, AWS Lambda, Test Automation, Single Sign-on (SSO), Web3, UI Libraries, GitHub, Hasura, OpenAI GPT-3 API, OpenAI GPT-4 API, Figma, Single-page Applications (SPA)

Back-end Node.js Developer

2018 - 2018

SPARK!

Created a system to render arbitrary HTML into 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, HTML, CSS, JavaScript, Front-end, HTML5, REST APIs, Jest, Back-end, PostgreSQL, Amazon Web Services (AWS), Payment APIs, Full-stack Development, Third-party APIs, Express.js, Microservices, Redis, API/Services Architecture, API Design, ESLint, Kubernetes, API Integration, UI Libraries, GitHub, Hasura, Single-page Applications (SPA)

Front-end Developer

2018 - 2018

Terrashow

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, HTML, CSS, JavaScript, Front-end, HTML5, REST APIs, TypeScript, Responsive UI, Full-stack Development, Third-party APIs, Responsive Design, ESLint, API Integration, UI Libraries, GitHub, Hasura, Single-page Applications (SPA)

Full-stack Node.js and React Developer

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, HTML, CSS, JavaScript, Front-end, HTML5, REST APIs, GraphQL, Apollo, TypeScript, Jest, Back-end, Full-stack, PostgreSQL, Amazon Web Services (AWS), Payment APIs, Admin Panels, Full-stack Development, Third-party APIs, Responsive Design, UI Components, Microservices, API/Services Architecture, API Design, ESLint, Kubernetes, CI/CD Pipelines, API Integration, UI Libraries, GitHub, Hasura, Single-page Applications (SPA)

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, HTML, CSS, JavaScript, Front-end, HTML5, REST APIs, Jest, Responsive UI, Admin Panels, Full-stack Development, Third-party APIs, Responsive Design, UI Components, API/Services Architecture, API Design, ESLint, Kubernetes, CI/CD Pipelines, API Integration, UI Libraries, GitHub, Hasura, Single-page Applications (SPA)

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, HTML, CSS, JavaScript, Front-end, HTML5, REST APIs, Jest, Responsive UI, Full-stack Development, Third-party APIs, Responsive Design, UI Components, ESLint, API Integration, UI Libraries, GitHub, Single-page Applications (SPA)

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, HTML, CSS, JavaScript, Front-end, HTML5, REST APIs, GraphQL, Apollo, Jest, Responsive UI, PostgreSQL, Admin Panels, Full-stack Development, Third-party APIs, Responsive Design, UI Components, API/Services Architecture, API Design, ESLint, CI/CD Pipelines, API Integration, UI Libraries, GitHub, Hasura, Single-page Applications (SPA)

Freelance Web Developer

2016 - 2017

Techstars.com (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, HTML, Front-end, HTML5, REST APIs, Back-end, Responsive UI, Full-stack, Full-stack Development, Third-party APIs, Responsive Design, API/Services Architecture, API Design, ESLint, API Integration, UI Libraries, GitHub

Freelance Ember.js Developer

2016 - 2016

100yea.rs (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, HTML, CSS, JavaScript, Front-end, HTML5, REST APIs, Responsive UI, Full-stack, Analytics, Full-stack Development, Third-party APIs, Responsive Design, UI Components, API/Services Architecture, API Design, ESLint, API Integration, UI Libraries, GitHub, Single-page Applications (SPA)

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, HTML, CSS, JavaScript, Front-end, HTML5, REST APIs, Back-end, Responsive UI, Full-stack, PostgreSQL, Admin Panels, Analytics, Full-stack Development, Third-party APIs, Responsive Design, API Design, ESLint, API Integration, UI Libraries, GitHub, Single-page Applications (SPA)

Freelance Front-end Developer

2015 - 2015

100yea.rs (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, HTML, HTML5, REST APIs, Responsive UI, Full-stack, Analytics, Full-stack Development, Third-party APIs, Responsive Design, API Design, ESLint, API Integration, UI Libraries, GitHub

Full-stack Web Developer

2014 - 2015

CarlsDesk

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, HTML, CSS, JavaScript, Front-end, HTML5, REST APIs, Back-end, Responsive UI, Full-stack, PostgreSQL, Admin Panels, Analytics, Full-stack Development, Third-party APIs, API Integration, UI Libraries

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, HTML, CSS, JavaScript, HTML5, REST APIs, Back-end, Full-stack, Admin Panels, Full-stack Development

Full-stack Developer

2012 - 2013

EventNow

Merged their three different back ends into one system.
Implemented the design and features of "version 2" of the site.
Performed DevOps on multiple platforms and their respective systems.
Created automation systems for backups/emails, etc.
Created data-based insights via statistical analysis.

Technologies: Front-end, MySQL, PHP, HTML, CSS, JavaScript, HTML5, REST APIs, Back-end, Full-stack, Analytics, Full-stack Development

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

Freelance

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, HTML, CSS, JavaScript, HTML5, REST APIs, Back-end, Auth0, Payment APIs, Admin Panels, Full-stack Development

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

Experience

Pramda: Practical Functional Programming in PHP

https://github.com/kapolos/pramda

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

https://github.com/kapolos/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.

Publication

Linux Best Practices and Tips by Toptal Developers

https://www.toptal.com/linux/tips-and-practices

Skills

Languages

CSS, PHP, HTML5, JavaScript, ECMAScript (ES6), TypeScript, HTML, GraphQL, SQL, Less, Haml, Visual Basic .NET (VB.NET), ES7, Sass, Bash Script, PureScript, Java, Python

Frameworks

Express.js, Ember.js, Bootstrap 3, Jest, React Native, Redux, Next.js, Electron, Tailwind CSS, .NET, NestJS

Libraries/APIs

React, Ember Data, jQuery, Node.js, REST APIs, MobX, JSON API, WebRTC, Google APIs, Google API, Amazon EC2 API, Twitter API, Facebook API, Amazon API, Web3.js, React Redux, TensorFlow

Tools

PHP-FPM, Apache, NGINX, Stylus, Figma, Varnish, GitHub, Git, PhpStorm, Brunch, Gulp, Grunt, Sequelize, Vagrant, Auth0, Amazon Cognito, Sentry, WebStorm, Appcelerator, Emacs, SaltStack, Ansible, MATLAB, Adobe Photoshop, Appcelerator Titanium

Paradigms

Asynchronous Programming, Promise, Responsive, Responsive Web Design (RWD), API/Services Architecture, Test Automation, Functional Programming, Object-oriented Programming (OOP), Microservices

Platforms

Linux, Amazon Web Services (AWS), Kubernetes, AWS Lambda, Blockchain, Docker, WordPress, Safari, Windows, Amazon Linux, Azure

Storage

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

Other

Ember CLI, Apollo, Back-end, Responsive UI, Full-stack, Admin Panels, Analytics, Full-stack Development, Third-party APIs, Responsive Design, UI Components, API Design, ESLint, API Integration, Web3, OpenAI GPT-3 API, OpenAI GPT-4 API, Single-page Applications (SPA), Serverless, Ubuntu Server, GNU, Cryptocurrency Wallets, Payment APIs, CI/CD Pipelines, Single Sign-on (SSO), UI Libraries, Artificial Intelligence (AI), Front-end, Finance, Statistics, Graph Theory, Calculus, Algebra, Geometry, Optimization, Chrome Extensions, Browser Automation, PDF, Rendering, Windows Subsystem for Linux (WSL), HAProxy, Ethers.js, Crypto, APIs, PWA

Education

2018 - 2022

Master's Degree in Software Engineering

Harvard Extension School - Cambridge, MA, USA

2005 - 2007

Master of Science Degree in Economic Theory and Policy

University of Crete - Crete

2000 - 2004

University Degree in Applied Mathematics

University of Crete - Crete

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