Kostas is available for hire

Kostas Familonidis

Verified Expert in Engineering

Full-stack Developer

Location

Pireas, Piraeus, Greece

Toptal Member Since

June 18, 2014

Kostas is a seasoned full-stack engineer with 10+ years of experience developing web applications using Ruby, JavaScript, and Node.js in multiple sectors. He recently focused on SaaS integrations, internationalization projects, and cross-platform mobile application development. He is experienced with various projects and platforms, from business process automation to finance and beyond. Kostas has project management experience in the software industry and can drive teams to success.

Web Development Back-end Computer Science Code Review Full-stack Webhooks Back-end Development Full-stack Development Front-end SaaS Customer Relationship Management (CRM)Single Sign-on (SSO)Ruby on Rails (RoR)Ruby JSON Redmine Redis

Portfolio

FieldPulse

Ruby, Requirements Analysis, Project Timelines, Project Planning...

Getaway House

Ruby, JavaScript, API Integration, Full-stack, Ruby on Rails (RoR), HTML...

Procore

RSpec, Functional Programming, Unix, Object-oriented Programming (OOP), HTML...

Experience

Ruby on Rails (RoR) - 12 years Ruby - 12 years RSpec - 10 years JavaScript - 9 years Full-stack - 8 years React - 7 years Node.js - 7 years D3.js - 1 year

Availability

Full-time

Preferred Environment

Unix, Linux

The most amazing...

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

Work Experience

Ruby Developer

2024 - PRESENT

FieldPulse

Optimized existing codebase based on metrics analysis using RoR (Ruby on Rails).
Improved feature development that relies on real-time user interactions with the application servers.
Participated in the planning of new features and optimization tasks.

Technologies: Ruby, Requirements Analysis, Project Timelines, Project Planning, Discovery Workshops, Code Review

Full-stack Web Developer

2021 - 2023

Getaway House

Developed the application stack for enabling multiple payment processors Stripe, and Braintree, using Ruby, Ruby on Rails (RoR), JavaScript, and React.
Improved code quality to support message queuing under the CQRS pattern.
Designed robust services based on task-based UI (user interface) analysis.
Integrated 3rd-party platforms API such as Twillio and Zendesk.
Provided accurate estimates with scope analysis and management to provide state-of-the-art delivery standards.
Designed and implemented custom solutions for improving the customer UX (user experience), such as waitlists and a loyalty program.
Implemented TDD (test-driven development) and extensive acceptance-test coverage in line with Agile development practices.

Technologies: Ruby, JavaScript, API Integration, Full-stack, Ruby on Rails (RoR), HTML, Architecture, Back-end Development, Customer Relationship Management (CRM), Back-end, Zendesk, Stripe API, Auditing, Web Development, Node.js, JSON, Deployment, RSpec, Project Management, React, Axios, Full-stack Development, Stripe, BrainTree, System Architecture, Agile, Twilio, Heroku, CI/CD Pipelines, Front-end, Bootstrap, Booking, Requirements Analysis, Project Timelines, Project Planning, Discovery Workshops, Code Review

Full-stack Web Developer

2019 - 2021

Procore

Developed the application's stack to support internationalization across the platform.
Modernized existing parts of the codebase using the latest Ruby and JavaScript patterns, RSpec, and UI (user interface) functional testing.
Performed auditing and regression tests analysis on tools enforcing internationalization and localization standards.
Reviewed code and supported the team's internal QA (quality assurance) process.
Led the engineering team to document and apply code best practices across the organization.
Implemented TDD (test-driven development) and extensive acceptance-test coverage in line with Agile development practices.

Technologies: RSpec, Functional Programming, Unix, Object-oriented Programming (OOP), HTML, Git, Redis, JavaScript, Ruby on Rails (RoR), Ruby, React, Webhooks, Full-stack, Node.js, APIs, SaaS, Code Architecture, REST APIs, API Integration, Architecture, Back-end Development, Back-end, TypeScript, Auditing, Stripe, Storybook, Jest, Web Development, JSON, Cypress, Deployment, Project Management, Axios, Full-stack Development, Express.js, Agile, Front-end, Requirements Analysis, Project Timelines, Project Planning, Discovery Workshops, Code Review

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.
Reviewed code and supported the team's internal QA (quality assurance) process.
Implemented TDD (test driven development) with Agile development practices.
Provided accurate time estimates with delivery with the team.

Technologies: Functional Programming, Unix, HTML, CSS, JavaScript, React Native, React, Webhooks, Node.js, Project Management, APIs, Code Architecture, Redux, Redux-Saga, REST APIs, Architecture, Material UI, Web Development, JSON, Deployment, Axios, Full-stack Development, Express.js, Agile, Android, iOS, Front-end, Requirements Analysis, Project Timelines, Code Review

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.
Provided scope analysis and execution plan in line with industry best practices.

Technologies: Unix, Object-oriented Programming (OOP), Git, GraphQL, React, Ruby on Rails (RoR), Ruby, Webhooks, Full-stack, Node.js, APIs, SaaS, Code Architecture, Redux, Redux-Saga, Architecture, Back-end Development, Back-end, Web Development, Deployment, Full-stack Development, System Architecture, Agile, Project Planning, Code Review

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.
Managed maintained the project's scope, and planned according to the customer needs.
Implemented TDD (test driven development) with Agile development practices using RSpec.

Technologies: RSpec, Functional Programming, Unix, Object-oriented Design (OOD), Object-oriented Programming (OOP), Ubuntu, Rack, HTML, TeamCity, Git, SQL, Redis, jQuery, Sinatra, Ruby, Webhooks, APIs, SaaS, REST APIs, Architecture, Back-end, Web Development, JSON, Deployment, Axios, Agile, CI/CD Pipelines, Requirements Analysis, Project Planning, Code Review

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: RSpec, Functional Programming, Object-oriented Design (OOD), Unix, Ubuntu, GitLab, Sinatra, Elasticsearch, Redmine, HTML, Memcached, D3.js, Git, SQL, MySQL Daemon, Redis, jQuery, Red Hat Linux, CSS, JavaScript, Ruby on Rails (RoR), Ruby, Webhooks, Full-stack, Project Management, APIs, SaaS, Code Architecture, REST APIs, API Integration, Architecture, Customer Relationship Management (CRM), Back-end, Web Development, JSON, Deployment, MongoDB, Full-stack Development, Corporate Finance, System Architecture, Agile, Rails Engines, Finance, Front-end, Bootstrap, Requirements Analysis, Project Timelines, Project Planning, Discovery Workshops, Code Review

Software Developer

2013 - 2013

Farncobe

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 using RSpec.

Technologies: RSpec, Object-oriented Design (OOD), Unix, PostgreSQL, Ubuntu, HTML, Git, SQL, Redis, Ruby on Rails (RoR), Ruby, Webhooks, APIs, SaaS, REST APIs, API Integration, Back-end, Web Development, JSON, Single Sign-on (SSO), Deployment, Project Management, Agile, CI/CD Pipelines, Bootstrap, Requirements Analysis, Project Timelines, Project Planning

PMO/Projects Coordinator

2008 - 2012

Intrasoft International

Oversaw SLA budgets in accordance with EU general directives.
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, Git, MySQL Daemon, CSS, HTML, SQL, Ruby, Bash, Red Hat Linux, Project Management, Customer Relationship Management (CRM), Web Development, JSON, Corporate Finance, Project Timelines, Project Planning

Experience

Basic Skeleton for an Object-oriented JavaScript Framework

https://gist.github.com/kfamilonidis/200221fb1fa6373c778dc3997c94d4d8

I undertook the task of creating a fundamental framework for object-oriented JavaScript programming. My focus was on minimalistic object initialization, emphasizing scope management and extensibility. The initialization function is activated by a self-executing anonymous function which I designed to transfer the scope to the initialization method within the object. This design approach enables the creation of multiple objects while ensuring a significant reduction in scope, enhancing efficiency and clarity.

React and React Native

Developed and enhanced user experiences of multiple forum sites utilizing React and React Native frameworks so the end codebase was shared between web, mobile, and native devices. The solution improved the general organization of the project and the users' UI.

GraphQL Implementation

Built a GraphQL implementation from scratch to utilize very complex data structures and report statistics with minimum time delay. Developed both back- and front-end logic that delivered a complete solution.

Basic Setup for Loading TSort in Ruby

https://gist.github.com/kfamilonidis/e193240de686c7971505e582845e0e04

Topological sorting or TSort is a built-in method in Ruby 3.1. Its capability is to solve complex dependency problems that can be represented as graphs. One of its uses is in library dependencies resolution, but its use can be extended to many fields, such as task management.

Skillset

Languages

HTML, GraphQL, JavaScript, CSS, Ruby, HTML5, Bash, SQL, TypeScript, Python

Frameworks

React Native, Sinatra, Ruby on Rails (RoR), Redux, Express.js, Bootstrap, Material UI, Next.js, Jest, Cypress

Libraries/APIs

React, jQuery, Node.js, Redux-Saga, REST APIs, Stripe API, Stripe, Rails Engines, Rack, D3.js

Tools

RSpec, Git, TeamCity, Redmine, GitLab

Paradigms

Object-oriented Programming (OOP), Object-oriented Design (OOD), Agile, Functional Programming, Metaprogramming, Requirements Analysis

Platforms

Linux, Ubuntu, Red Hat Linux, Heroku, Unix, Zendesk, Android, iOS, Twilio

Storage

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

Other

Webhooks, Full-stack, APIs, SaaS, Code Architecture, API Integration, Architecture, Back-end Development, Customer Relationship Management (CRM), Back-end, Auditing, Web Development, Single Sign-on (SSO), Deployment, Computer Science, Axios, Full-stack Development, Corporate Finance, System Architecture, Finance, Front-end, Project Timelines, Project Planning, Code Review, Artificial Intelligence (AI), CI/CD Pipelines, Booking, Discovery Workshops, Storybook, Machine Learning, BrainTree

Industry Expertise

Project Management

Education

2000 - 2004

BSc Degree in Business Administration (Technology)

University of Patras - Patras, Greece

Certifications

JULY 2020 - PRESENT

AI Programming with Python Nanodegree

Udacity

SEPTEMBER 2012 - SEPTEMBER 2015

Red Hat Linux System Administrator

Red Hat

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