Pantelis Vratsalis, Software Developer in Athens, Central Athens, Greece
Pantelis Vratsalis

Software Developer in Athens, Central Athens, Greece

Member since November 19, 2013
Pantelis loves coding and helping teams grow their skills. He's a polyglot engineer specializing in Java, Scala, Python, Ruby, JavaScript, PHP, and other tried and tested tools and frameworks, including React and Vue. He enjoys working with complex codebases and big data and has experience using the right tools for the job.
Pantelis is now available for hire


  • Glispa
    Java, Scala, Vert.x, Kafka, Druid, Kubernetes, NodeJS, GraphQL
    Ruby on Rails, React, PostgreSQL
  • Anyroad
    Ruby on Rails, React, PostgreSQL



Athens, Central Athens, Greece



Preferred Environment

Linux, Vim, VS Code, Git, Python, Ruby, Java

The most amazing...

...thing I've coded is a retargeting DSP for programmatic advertising. It was a great challenge due to the traffic scale (150,000 reqs/second) and complexity.


  • Senior engineer / tech lead

    2017 - 2020
    • Working with a variety of technologies (Java/Scala & Vert.x, Kafka, Aerospike) in the context of retargeting (dynamic audience segmentation and personalized ads). Working with big data for analytics and reporting (hadoop, hive, spark, flink, presto and druid).
    • Working with NodeJS for building APIs (GraphQL) that power UIs for reporting and campaign management purposes.
    • Deploying and scheduling applications using Docker, Nomad, Consul and Kubernetes.
    Technologies: Java, Scala, Vert.x, Kafka, Druid, Kubernetes, NodeJS, GraphQL
  • Tech lead

    2016 - 2017
    • Co-founder and tech lead. Technologies used: Ruby on rails for backend API, ReactJS for frontend, PostgreSQL, Redis, Roda (ruby microframework) for landing pages / marketing site..
    • Integrated multiple external services for email, sms, geolocation etc (Twilio, Nexmo, Sendgrid, Mailgun etc).
    Technologies: Ruby on Rails, React, PostgreSQL
  • Senior software engineer

    2015 - 2016
    • Worked with a team of 6 developers to build the dashboard and front pages of experience booking (tour guides etc).
    • Built a single-page application with React and a ruby on rails back-end.
    Technologies: Ruby on Rails, React, PostgreSQL
  • Full Stack Web Developer

    2014 - 2015
    • Was responsible for most of the features of the website (API development and front-end AngularJS work).
    • Worked in a small team of 3 reporting directly to the CEO.
    • Worked both on back-end (PHP Yii framework, MongoDB) and front-end (Angular 1.4).
    Technologies: PHP, AngularJS
  • Web Developer & Team lead

    2013 - 2014
    • Worked as a contractor for a Swiss online learning platform for sales people. Developed the platform in Python with the Pyramid framework.
    • Worked as a developer for a social WiFi startup. Built several aspects of the application visible to visitors as well as the control panel for clients (WiFi network owners).
    • Worked as a team leader with Stratagem Technologies Ltd. Technologies used: python, nodejs, angularjs, mongodb, redis. Big data on sports betting industry, used for statistical analyses and other purposes. Managed a distributed team of 6 developers. Built and maintained REST APIs and API consumers, too (using Python).
    Technologies: Python, Pyramid, pytest, ZombieJS, Selenium, AngularJS, PHP, PHPUnit
  • Web Developer

    2008 - 2012
    • Developed several projects as a freelancer. Created a startup company for online market research.
    • Created brochure websites for several clients using Wordpress.
    • Created an online polls web application.
    Technologies: PHP, WordPress, CodeIgniter, Kohana


  • Online market research project (Development)

    Currently the website has suspended its functions. This website was online for 3 years (beginning 2011 till the end of 2013) for an online market research firm, but it has currently suspended its functions. It had a panel to recruit online members (around 4000 members). I created this as a startup venture, and developed both the front and back-end (admin interface and user interface). I also handled marketing efforts (SEO and SEM). The web application was developed with PHP and CodeIgniter, and the data was stored using MySQL.

  • Online polls website (Development)

    This project enables the creation of web polls and subsequent embedding of them on a website. It is also capable of obtaining the URL/link/QR code of the poll to share it and get responses. The project has been developed with PHP and the Kohana framework and uses MySQL for storing data.

  • Eduno (Development) is an online learning platform for salespeople based in Switzerland. It allows companies and individuals to educate themselves in sales related subjects with online videos and interactive quizzes. It also has a recommendation engine for marketing purposes. I'm working on the development team of this ongoing project with 6 remote individual contractors. Development is in Python with the Pyramid framework. For storage, we used the ZODB NoSQL database.

  • Collection Feature for Freelancer Platform (Other amazing things)

    I developed the collections feature for an online platform for freelance developers, displaying curated collections of freelancer services. It includes an administrative interface where services are grouped into collections. Freelancers can request to be included in one or more collections.

  • Quovoo quotes API (Development)

    Famous quotes API, available through Rapid API marketplace. Technologies used: Fastify (nodejs) for backend with a PostgreSQL database.

  • AskBeat shopify app (Development)

    AskBeat easy email NPS surveys is a shopify app for sending NPS surveys to store customers. The surveys are sent via email either manually (uploading a list of customers) or automatically every time an order is placed (integrating with the API of shopify). Technologies used: Ruby on rails (backend), Vuejs (SPA frontend), Bulma (css).

  • Vegetarian Keto Recipes android app ( Recipeno ) (Development)

    A native android mobile app for vegetarian keto recipes. Built with Java and communicates with an API built with ruby on rails for fetching data.

  • (Development) is a local theater performances search engine. Visitors can easily search among theaters and performances, using multiple criteria (e.g. genre, day of week) and find performances that interest him/her.

    Technologies used: Ruby on rails 5, jQuery & vanilla Javascript, SQLite 3, SASS, webpack for assets bundling. Integrations with Mailgun's API and with various affiliate APIs.


  • Languages

    Python, Ruby, Java, Scala, GraphQL, JavaScript, PHP
  • Frameworks

    Ruby on Rails (RoR), Pyramid, Laravel, Bootstrap, Mockery, Flask
  • Libraries/APIs

    React, Vue.js, Mandrill API, jQuery, Handlebars, MailChimp API, Facebook API, PayPal API
  • Tools

    Google Analytics, MailChimp, Mantis, Terminal, PhpStorm, Vim Text Editor, Git, GitHub, Amazon SQS, Capistrano
  • Paradigms

    Object-oriented Programming (OOP), Test-driven Development (TDD), Responsive Web Design (RWD), Class-based OOP, Unit Testing, SOLID Principles, REST, Agile Software Development, Scrum, Pair Programming, Inversion of Control, Design Patterns, Behavior-driven Development (BDD)
  • Platforms

    Apache Kafka, Ubuntu, Linux, Amazon Web Services (AWS)
  • Storage

    PostgreSQL, Aerospike,, MongoDB, MySQL
  • Other

    Ajax, Math, Web Services, OAuth


  • MBA degree in Business Administration
    2003 - 2003
    Rotterdam School of Management - Rotterdam, Netherlands (exchange program)
  • MBA degree in Business Administration
    2001 - 2003
    Athens University of Economics and Business - Athens, Greece
  • B.Sc. degree in Physics
    1997 - 2001
    University of Crete - Heraklion, Greece

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