Kostas Familonidis, Software Developer in London, United Kingdom
Kostas Familonidis

Software Developer in London, United Kingdom

Member since November 21, 2013
Kostas is a passionate full-stack developer, most recently focused on cross-platform mobile app development but also experienced with a variety of other projects and platforms, from business process automation to finance and beyond.
Kostas is now available for hire




London, United Kingdom



Preferred Environment

Unix, Linux

The most amazing...

...thing I've developed is a CRM that integrates mail services in mobile devices.


  • Full-stack Web Developer

    2019 - PRESENT
    Procore Technologies, Inc.
    • Developed the application's stack to support internationalization across web platform.
    • Reviewed code and supported the team's internal QA (Quality Assurance) process.
    • Modernized existing parts of the application's codebase using the latest patterns.
    • Implemented TDD (Test Driven Development) and extensive acceptance-test coverage in-line with Agile development practices.
    Technologies: Functional Programming, Unix, Object-oriented Programming (OOP), HTML, Git, Redis, JavaScript, Ruby on Rails (RoR), Ruby, React
  • React Developer

    2016 - 2018
    Vertical Scope, Inc.
    • Developed cross-platform native mobile applications in iOS and Android using JavaScript and React Native.
    • Developed and integrated React components into a forum website using Redux architecture.
    • Improved UX (User Experience) and UI (User Interface) performance on mobile applications.
    • Implemented TDD (Test Driven Development) with Agile development practices.
    Technologies: Functional Programming, Unix, HTML, CSS, JavaScript, React Native, React
  • Full-stack Web Developer

    2017 - 2017
    Pivot.io, Inc.
    • Developed an application for automating business processes in Ruby, Ruby on Rails, JavaScript, and GraphQL.
    • Developed and integrated React components using Redux and sagas for concurrent data structures.
    • Transitioned REST (Representational State Transfer) APIs and micro-services in GraphQL implementations.
    Technologies: Unix, Object-oriented Programming (OOP), Git, GraphQL, React, Ruby on Rails (RoR), Ruby
  • Software Engineer

    2015 - 2015
    Sky UK, Ltd.
    • Developed full-stack applications using microservices in Ruby, Sinatra, and JavaScript.
    • Utilized A/B testing to validate product efficiency on customer retention rates.
    • Maintained and developed multiple custom rack middlewares in Ruby.
    • Implemented TDD (Test Driven Development) with Agile development practices..
    Technologies: Functional Programming, Unix, Object-oriented Design (OOD), Object-oriented Programming (OOP), Ubuntu, Rack, HTML, TeamCity, Git, SQL, Redis, jQuery, Sinatra, Ruby
  • Lead Developer

    2013 - 2015
    Ringley, Ltd.
    • Developed full-stack applications on the intranet/extranet deployed to the cloud.
    • Handled back-end system administration and infrastructure configuration to prepare for distributed computing.
    • Developed a contract management system for tracking job completion and staff performance.
    • Implemented and designed a back-end storage system for optimized performance in MongoDB and MySQL.
    • Implemented and designed an Elasticsearch cloud-based search engine solution.
    • Modernized existing Ruby on Rails applications by extracting business logic, using unit testing, and making use of JavaScript, Ruby, and Ruby on Rails engines.
    • Exposed secure web APIs to integrate with mobile applications.
    • Developed a financial application that monitors and calculates cash flows, payments fees, and percentage fees.
    • Restructured and introduced effective project management methodologies in the organization.
    Technologies: Functional Programming, Object-oriented Design (OOD), Ember.js, Unix, Ubuntu, GitLab, MongoDB, Sinatra, Elasticsearch, Redmine, HTML, Memcached, D3.js, Git, SQL, MySQL Daemon, Redis, jQuery, Red Hat Linux, CSS, JavaScript, Ruby on Rails (RoR), Ruby
  • Software Developer

    2013 - 2013
    • Developed a back-end authentication system for a mobile application.
    • Integrated Facebook and Twitter API on the application UI.
    • Developed a full database-driven implementation for multi-language support.
    • Implemented TDD (Test Driven Development) and extensive acceptance-test coverage.
    Technologies: Object-oriented Design (OOD), Unix, PostgreSQL, Ubuntu, HTML, Git, SQL, Redis, Ruby on Rails (RoR), Ruby
  • PMO/Projects Coordinator

    2008 - 2012
    Intrasoft International
    • Oversaw SLA budgets.
    • Maintained the database backlog for tracking work in progress using Ruby, MySQL, and Linux.
    • Consolidated contracts and delivery of technical documents.
    • Produced and maintained all project documentation, including project plan and project scope.
    • Organized, prepared, and followed up the invoicing procedure, including infrastructure procurement and software license updates.
    Technologies: Linux, Redmine, OLAP, Git, MySQL Daemon, CSS, HTML, SQL, Ruby, Bash, Red Hat Linux


  • React and React Native (Development)

    Developed and enhanced user experiences on multiple forum sites utilizing React and React Native frameworks.

  • GraphQL Implementation (Development)

    Built a GraphQL implementation from scratch for utilizing very complex data structures and reporting statistics with minimum time delay.


  • Languages

    HTML, JavaScript, Ruby, HTML5, Bash, SQL, CSS, GraphQL
  • Frameworks

    React Native, Sinatra, Ruby on Rails (RoR), Ember.js
  • Libraries/APIs

    Mongoid, React, jQuery, Rack, D3.js
  • Tools

    Git, TeamCity, Redmine, GitLab
  • Paradigms

    Object-oriented Programming (OOP), Object-oriented Design (OOD), Functional Programming, Metaprogramming, OLAP
  • Platforms

    Linux, Ubuntu, Red Hat Linux, Unix
  • Storage

    Elasticsearch, Redis, MongoDB, MySQL Daemon, PostgreSQL, Memcached


  • BSc degree in Business Administration (Technology)
    2000 - 2004
    University of Patras - Patras, Greece


  • Red Hat Linux System Administrator
    Red Hat

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