Haroldas Mackevicius, Developer in Amsterdam, Netherlands
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Haroldas Mackevicius

Bio

Haroldas is a full-stack data specialist with over eight years of experience in data analytics, machine learning engineering, data engineering, and analytics engineering. He has led and delivered machine learning projects that drastically improved KPIs. Currently, Haroldas helps startups that want to become more data-driven and find product-market fit by engineering data pipelines that combine multiple data sources and deliver insights through analyses, dashboards, and modelling.

Portfolio

ISM University of Management and Economics
University Teaching, Python, SQL, Machine Learning
Vinted
Python, SQL, Data Build Tool (dbt), Spark, Machine Learning, Looker...

Experience

  • SQL - 8 years
  • Python - 8 years
  • Analytics - 8 years
  • Statistics - 8 years
  • Supervised Learning - 5 years
  • Machine Learning - 5 years
  • Data Engineering - 3 years
  • Data Build Tool (dbt) - 2 years

Preferred Environment

Slack, Cursor AI, Visual Studio Code (VS Code), Microsoft Teams

The most amazing...

...thing I've developed is a machine learning model for classifying counterfeit items that reduced user reports by over 75%.

Work Experience

Visiting Lecturer

2025 - PRESENT
ISM University of Management and Economics
  • Developed and led an introduction to data science course for second-year bachelor students of the Economics and Analytics program.
  • Created the course materials, i.e., Jupyter notebooks for lectures and seminars, three homework assignments on publicly available datasets, a group project assignment, and two exams.
  • Guided students on group projects focused on experiencing the full data science project cycle, including dataset selection, data cleaning and preparation, model training, and results display in a dashboard.
Technologies: University Teaching, Python, SQL, Machine Learning

Senior Data Scientist

2020 - 2025
Vinted
  • Reduced user reports of counterfeit items by 75% by fine-tuning and deploying a BERT-based model that classified counterfeit items from titles and descriptions.
  • Developed a machine learning classifier and the data pipelines for filtering out malicious accounts from company metrics, guaranteeing interpretability of metrics across the various domains within the company, e.g. finance and marketing.
  • Headed internal efficiency projects within the data science and analytics function, such as Jupyter Notebooks peer review, automated via GitHub Actions.
Technologies: Python, SQL, Data Build Tool (dbt), Spark, Machine Learning, Looker, Data Engineering, Analytics, Natural Language Processing (NLP), Supervised Learning, Docker, Analysis, Statistics

Experience

LLM-based Data Science Learning Tool

A Streamlit application that allowed students to respond to multiple-choice and open-ended questions and helped them understand their mistakes. The LLM used extracts from data science textbooks when answering, employing retrieval-augmented generation.

Education

2015 - 2019

Bachelor's Degree in Economics and Politics

ISM University of Management and Economics - Vilnius, Lithuania

Skills

Tools

Looker, Slack, Microsoft Teams

Languages

SQL, Python

Frameworks

Spark, Streamlit

Platforms

Docker, Visual Studio Code (VS Code)

Other

Analysis, Machine Learning, Analytics, Supervised Learning, Statistics, Data Build Tool (dbt), Data Engineering, Economics, Natural Language Processing (NLP), LangChain, Education, Cursor AI, University Teaching

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