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

Software Developer in Athens, Central Athens, Greece

Member since January 8, 2014
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


  • AskBeat
    Prometheus, Vue, React, Ruby on Rails (RoR)
  • Glispa
    GraphQL, Node.js, Kubernetes,, Presto DB, Flink, Spark, Apache Hive...
    PostgreSQL, React, Ruby on Rails (RoR)



Athens, Central Athens, Greece



Preferred Environment

Java, Ruby, Python, Git, Visual Studio Code (VS Code), Vim Text Editor, Linux

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.


  • Tech Lead

    2019 - PRESENT
    • Co-founded and tech-led AskBea, a Shopify partner that builds apps to help store owners grow their sales and better manage their store.
    • Handled the first Shopify app, a post-purchase and abandoned cart NPS survey scheduling and reporting software.
    • Used machine learning for building the recommendation algorithm for the second app, a product recommendation engine.
    Technologies: Prometheus, Vue, React, Ruby on Rails (RoR)
  • Senior Engineer and Tech Lead

    2017 - 2019
    • Worked on retargeting dynamic audience segmentation and personalized ads using Java, Scala, Vert.x, Kafka, Aerospike, and big data for analytics and reporting.
    • Built APIs that power UIs for reporting and campaign management purposes using Node.js and GraphQL.
    • Deployed and scheduled web applications using Docker, Nomad, Consul, and Kubernetes.
    Technologies: GraphQL, Node.js, Kubernetes,, Presto DB, Flink, Spark, Apache Hive, Hadoop, Apache Kafka, Vert.x, Scala, Java
  • Tech Lead

    2016 - 2017
    • Co-founded and led technical projects. Used technologies including Ruby on Rails for the back-end APIs, React for the front end, PostgreSQL, Redis, and Roda for the landing pages and marketing website.
    • Integrated multiple external services for things like email, SMS, geolocation (e.g., Twilio, Nexmo, Sendgrid, Mailgun).
    Technologies: PostgreSQL, React, Ruby on Rails (RoR)
  • Senior Software Engineer

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

    2014 - 2015
    • Owned most of the features of the website (API development and front-end AngularJS work).
    • Collaborated with a small team of three reporting directly to the CEO.
    • Contributed to the development of the back end (PHP Yii framework, MongoDB) and front end (Angular 1.4).
    Technologies: Ansible, AngularJS, PHP
  • Web Developer and Team Lead

    2013 - 2014
    • Contracted for a Swiss online learning platform for sales people. Developed the platform in Python with the Pyramid framework.
    • Developed for a social wifi startup. Built several aspects of the application visible to visitors and the control panel for the clients (wifi network owners).
    • Led a team with Stratagem Technologies, Ltd. Technologies used include Python, Node.js, AngularJS MongoDB, and Redis. Used big data from the sports betting industry for statistical analyses and other purposes. Managed a distributed team of six developers. Built and maintained REST APIs and API consumers using Python.
    Technologies: PHPUnit, PHP, AngularJS, Selenium, Zombie.js, Pytest, Pyramid, Python
  • 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.
    • Built an online polls web application.
    Technologies: Kohana, CodeIgniter, WordPress, PHP


  • Online Market Research Project

    Currently, the website has suspended its functions. This website was online for three 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 4,000 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

    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 was developed with PHP and the Kohana framework and uses MySQL to store data.

  • Eduno 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 six remote individual contractors. Development is in Python with the Pyramid framework. For storage, we used the ZODB NoSQL database.

  • Collection Feature for Freelancer Platform

    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

    Famous quotes API, available through Rapid API marketplace. Technologies used: Fastify (Node.js) for the back end with a PostgreSQL database.

  • AskBeat Shopify App

    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 Shopify's API). Technologies used include Ruby on Rails, Vue.js, and Bulma.

  • Vegetarian Keto Recipes Android App (Recipeno)

    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.

  • is a local theater performance search engine. Visitors can easily search among theaters and performances, using multiple criteria (e.g., genre, day of the week), to find performances that interest them.

    Technologies used: Ruby on rails 5, jQuery and vanilla JavaScript, SQLite 3, Sass, and Webpack for asset bundling.

    Integrations were made 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, Zombie.js, Selenium, AngularJS, PHPUnit, CodeIgniter, Kohana, Vert.x, Hadoop, Spark, Presto DB, Flask
  • Libraries/APIs

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

    Google Analytics, Mailchimp, Mantis, Terminal, PhpStorm, Vim Text Editor, Git, GitHub, Pytest, Ansible, Flink, Amazon Simple Queue Service (SQS), Capistrano
  • Paradigms

    Object-oriented Programming (OOP), Test-driven Development (TDD), Responsive Web Design (RWD), Class-based OOP, Unit Testing, 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), WordPress, Kubernetes, Visual Studio Code (VS Code)
  • Storage

    PostgreSQL, Aerospike,, MongoDB, MySQL, Apache Hive
  • Other

    SOLID Principles, Mailchimp API, Ajax, Mathematics, Web Services, Prometheus, 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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