Andrii Kostenko, Developer in Helsinki, Finland
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Andrii Kostenko

Verified Expert  in Engineering

Software Developer

Helsinki, Finland
Toptal Member Since
June 17, 2013

Andrii is an accomplished software engineer experienced in creating large-scale, complex applications. He has worked both as a back-end and front-end engineer. He excels at planning and implementing intricate solutions to technical problems, including determining which technologies should be used.


AngularJS, RQ, Flask, Python
GeoDjango, Python
Backbone.js, JavaScript, Yii, PHP




Preferred Environment

Vim Text Editor, MacOS, Git, PyCharm

The most amazing...

...thing I've coded is an online commenting engine that handles millions of visitors per day.

Work Experience

Software Engineer

2014 - 2016
  • Gained knowledge of the American health insurance system.
  • Contributed to the composition of up to 70% of the project's test coverage.
  • Tried several XMPP solutions and created a high-load solution with ejabberd.
  • Wrote a Cron-like daemon for RQ.
  • Collaborated with team members in an Agile/Scrum environment, which increased productivity.
  • Improved ability to communicate with clients in English.
  • Created docker-based development environment, which allows new and current developers quickly setup required project infrastructure.
Technologies: AngularJS, RQ, Flask, Python


2010 - 2014
  • Created a custom world map using MapServer.
  • Created a number of fetchers from different sources.
Technologies: GeoDjango, Python


2013 - 2013
  • Converted a prototype with write-only code to a production-ready project, including working architecture and unit-tests (PHPUnit and Buster.JS)
  • Switched development to a Scrum-like process.
  • Founded a team of qualified software/QA engineers in Kyiv, Ukraine.
  • Replaced buggy code (built over two month of development) with a remote API of existing services.
  • Refactored and rewrote numerous project parts.
  • Covered code with JS/PHPUnit tests (over 180 tests created).
  • Administrated development/production servers.
Technologies: Backbone.js, JavaScript, Yii, PHP

Software Engineer

2012 - 2013
  • Chose the programming language and technology package for the company (Python/Django 1.4/Celery).
  • Created a CI environment with 1100 passing tests (tests were mostly for used applications)
  • Used a variety of public modules instead of writing redundant code, patching them if needed.
  • Created a large project with an efficient, clean code structure.
  • Created numerous bugreports in Django bugtracker with patches.
  • Developed a public API with Django Tastypie.
  • Improved Django Coffin so that it worked as a transparent template loader.
Technologies: Jinja, Celery, Django, Python

Software Engineer

2011 - 2011
  • Refactored a complex body of code, making it more supportable.
  • Created a cell phone website version of the code using jQuery Mobile.
Technologies: jQuery Mobile, Catalyst, Perl

Software Engineer

2009 - 2011
Rambler-Afisha Internet Holding
  • Developed highly-scalable internet applications
  • Optimized a database for high load processing.
  • Refactored a service handling over 10 million requests per day.
  • Improved the libpurple library to support a large number of accounts.
  • Improved the speed and code quality of existing code.
Technologies: PHP, PL/pgSQL, Node.js, C++, Catalyst, Perl

Software Engineer

2007 - 2009
  • Created a peer-to-peer money transfer application.
  • Developed a service to take 25 web site screenshots per second.
  • Created a sandbox for using compilers with online IDEs.
  • Used a partial MySQL master-master replication to create two interfaces: one was public with public data and one was private in a bank network with private data.
  • Created a complex administrator panel for payment transaction monitoring.
Technologies: C#, Lua, Perl


An online visa requirement database.

MyBook Online Library
This is my most interesting and successful project. It includes highly readable code, test coverage, and effective technologies.


A project that creates a tree from incoming and outgoing links.

A Russian ticket selling company.

Credit Card Number Generator

A simple valid credit card generator on GAE.


An online management assessment tool.

Concierge service for US health insurance
2006 - 2008

Partially Completed Degree in Appiled Mathematics

Dnipropetrovsk National University - Dnipropetrovsk, Ukraine

2004 - 2006

Graduate Degree in Software Engineering

IT Academy "Step" - Dnipropetrovsk


SQLAlchemy, Python-rq, jQuery Mobile, RQ, React, Node.js, DBIx::Class, jQuery, Backbone.js


Vim Text Editor, NGINX, Git, PyCharm, Ansible, Sequelize, Chef, Celery, Amazon Elastic Container Service (Amazon ECS), Zsh


Django, Flask, Catalyst, Jinja, GeoDjango, AngularJS, Yii


Perl, Python, SQL, JavaScript, PL/pgSQL, Lua, C#, CSS3, HTML5, PHP, C++, C


PostgreSQL, MySQL, Memcached, Redis, Amazon S3 (AWS S3), Amazon DynamoDB, PostGIS, Kyoto Tycoon


Test Automation, Scrum, Agile Software Development, Test-driven Development (TDD)


Docker, Linux, FreeBSD, Amazon EC2, MacOS



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