Drazen Zaric, Developer in Belgrade, Serbia
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Drazen Zaric

Verified Expert  in Engineering

Data Scientist and Machine Learning Developer

Belgrade, Serbia
Toptal Member Since
June 22, 2019

Drazen is a data scientist and data engineer with over seven years of experience building analytics infrastructure, machine learning, and data analysis. He has extensive experience in big data, machine learning, and web development. He has worked with notable companies such as Slack and Microsoft, and built products used by millions of users.


Tableau, Data Visualization, Data Science, Python, Redshift, Snowflake...
Freelance Consultant
Tableau, Big Data, SQL
Apache Impala, Hadoop, Aerospike, JavaScript, Python, Java, Product Management...




Preferred Environment

Vim Text Editor, Python, Linux, MacOS

The most amazing...

...project I've built was an analytics infrastructure for a product with 150 million users.

Work Experience

Data Scientist

2019 - 2020
  • Collaborated as a part of the data team. Developed dashboards in Tableau and data reports with Redash; worked on migrating from Redshift to Snowflake.
  • Supported the commercial and partnership teams with data insights.
  • Developed an interactive real-time map visualization of Teespring sales with JavaScript and Mapbox.
Technologies: Tableau, Data Visualization, Data Science, Python, Redshift, Snowflake, Data Analysis, MySQL, ETL, APIs, Dashboard Design, Dashboards, Interactive Maps, SQL, Big Data, Data Modeling, Database Modeling

Analytics Consultant

2019 - 2019
Freelance Consultant
  • Collaborated with small companies on establishing their data infrastructure, discipline, and teams.
  • Assessed existing processes, available data, and infrastructure.
  • Planned for future growth in terms of product and the team.
  • Helped with descriptive and predictive user behavior models, segmentation, and A/B testing.
Technologies: Tableau, Big Data, SQL

Product Manager

2017 - 2018
  • Led the team in developing Golden Boot, a game for a then-new platform called Facebook Instant Games. This product grew from an idea to over 10 million players in four months.
  • Oversaw product and project management, back-end development, data analysis, and game design within an Agile team.
  • Developed high-performance algorithms for matchmaking.
  • Created a distributed push notifications system backed by a Hadoop data warehouse and a machine learning model for user churn.
Technologies: Apache Impala, Hadoop, Aerospike, JavaScript, Python, Java, Product Management, App Product Management, Development, Agile, Scrum, Data Analysis, Lean Project Management

Data Scientist

2015 - 2017
  • Developed internal data products. Designed, developed, and deployed optimization algorithms for in-game tournament generation.
  • Created machine learning models for anomaly detection, product performance, and user behavior prediction tools for optimizing marketing campaigns.
  • Maintained and improved a custom, in-house BI tool.
  • Supported product managers, game designers, and user acquisition teams with analyses and insights.
Technologies: Pandas, NumPy, Scikit-learn, Flask, Tableau, SQL, Machine Learning, Python, Data Analysis, Databases, Database Analytics, PostgreSQL, Apache Impala, Data Visualization, Dashboard Design, Agile, Git, MySQL, Hadoop

Data Engineer

2013 - 2015
  • Developed and maintained an in-house ETL system and data warehouse on top of Hadoop and Impala for TopEleven, an online game with over 150 million players.
  • Transitioned a single PostgreSQL instance to an in-house Hadoop cluster solution.
  • Designed and wrote data import, SQL transformations, and oversaw the data quality.
  • Integrated data from internal and third-party data sources.
  • Scaled data warehouse and processes from a single product to multiple products.
Technologies: Hadoop, SQL, Python, Data Engineering, Apache Impala, PostgreSQL, MySQL, Data Analytics, Data Analysis, Linux, Bash, Git, Back-end, Databases, ETL, ETL Tools, ETL Testing, ETL Development, Data Modeling, Database Modeling

Software Development Engineer

2011 - 2013
  • Developed the PDF Reflow feature for Microsoft Word 2013.
  • Designed algorithms for converting a PDF into an editable DOCX document.
  • Implemented and evaluated machine learning models for identifying parts of a PDF document.
Technologies: C++, Algorithms, Software Engineering, Agile, Scrum


Blogboard is a search and discovery engine for official blogs of leading tech companies.

As a solo creator, I've worked on the front-end development in Vue.js, the back-end and search in Python, PostgresSQL, and Elasticsearch. I also wrote the official product blog.

Top Eleven by Nordeus

A highly successful online sports games, Top Eleven has had over 150 million players to date. I worked on the analytics infrastructure, product management, data science, and in-game algorithm development.

Votum Polls for Slack

This is a Slack app I developed end-to-end, enabling the polling and running of idea tournaments within Slack.

Selecta: An Amarok Player Extension

This is an inverted index and tf-idf retrieval engine for music in your library based off Last.fm tags. This was implemented from scratch in JavaScript, done back in the days when music was offline.

Improved Heatmaps in Python

This is a Python code, and a Jupyter notebook for an improved heatmap implementation using Matplotlib and Seaborn.

Similar to what you can easily get in Tableau using a Size parameter, here you can have a square as a parameter depending on the field value.

Described in detail in this blog post: https://towardsdatascience.com/better-heatmaps-and-correlation-matrix-plots-in-python-41445d0f2bec
2010 - 2011

Master's Degree of Science in Computer Science

University of Novi Sad - Novi Sad, Serbia

2006 - 2010

Bachelor's Degree in Computer Science

University of Novi Sad - Novi Sad, Serbia


Product Management Program

UC Berkeley Executive Education


Scikit-learn, Pandas, NumPy, Vue


Apache Impala, Tableau, Git, Ansible, Vim Text Editor, GitHub


Flask, Hadoop


Python, SQL, C++, JavaScript, Snowflake, Java, Bash


Data Science, Agile, Scrum, ETL


PostgreSQL, Aerospike, Redshift, Elasticsearch, MySQL, Databases, Database Modeling


Linux, MacOS, Apache Kafka


Data Engineering, Machine Learning, Algorithms, Data Analysis, Database Analytics, Data Visualization, Web Development, Optimization, eCommerce, Big Data, Front-end, Back-end, Writing & Editing, Software Engineering, Data Analytics, Dashboard Design, Product Management, App Product Management, Development, Lean Project Management, ETL Tools, ETL Testing, ETL Development, APIs, Dashboards, Interactive Maps, Data Modeling, Scraping, User Experience (UX), User Interface (UI), Data Scraping, Web Scraping

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