Oleksii Sliusarenko, Developer in Kiev, Ukraine
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Oleksii Sliusarenko

Verified Expert  in Engineering

Algorithms Developer

Kiev, Ukraine
Toptal Member Since
November 4, 2019

Oleksii is a senior research engineer specializing in machine learning with several years of hands-on, in-depth experience. In his free time, he competes in international programming and math competitions—and often wins. At Deloitte and Grammarly, he developed their core deep learning and AI algorithms. Oleksii has worked at all stages of R&D from problem formulation with clients to product deployment.


Abto Software
Docker, Rasa.ai, Scikit-learn, TensorFlow, Python
Natural Language Toolkit (NLTK), Keras, TensorFlow, Scikit-learn...
Amazon Web Services (AWS), OpenNLP, Keras, TensorFlow, Scikit-learn...




Preferred Environment

Machine Learning, Deep Learning, Natural Language Processing (NLP), Generative Pre-trained Transformers (GPT), Data Science

The most amazing...

...thing I've created was a practical algorithm to solve an open AI problem: detecting English sentences that make no sense.

Work Experience

Senior Research Engineer (Machine Learning, NLP)

2019 - 2020
Abto Software
  • Implemented a chatbot model designed for stable progressive learning for five years.
  • Reimplemented part of Rasa chatbot framework to fix OOM error and make it production-ready.
  • Found and fixed OOM error and experiment design problem in SoTA intent recognition paper.
Technologies: Docker, Rasa.ai, Scikit-learn, TensorFlow, Python

Senior Research Engineer (Machine Learning, NLP)

2017 - 2019
  • Implemented a contract classification algorithm with 95% accuracy which outperformed humans.
  • Developed a complex text summarization algorithm with 80% accuracy.
  • Created a company classification algorithm which increased human analytics quality by two times.
  • Completed all stages of complex text summarization problem including framing the problem, annotating the data, creating the model, deploying and supporting.
  • Organized data science hackathon which resulted in three new hires.
Technologies: Natural Language Toolkit (NLTK), Keras, TensorFlow, Scikit-learn, Machine Learning, Deep Learning, Data Science, Java, Python

Research Engineer (Machine Learning, NLP)

2013 - 2017
  • Developed a new sentence splitting component with 2X improvement in error rate.
  • Built an auto-correct feature with 99% accuracy compared to 90% existing version.
  • Implemented high-load storage with approximately 1,000,000 key-value requests per second per server.
  • Reimplemented contextual spell checker with 10x speed-up.
  • Implemented a practical solution with 99,9% specificity and 30% recall to an open problem of detecting sentences which don't make sense.
  • Processed petabyte-scale internet dump using Apache Spark for creating n-gram language models.
  • Prepared and conducted two courses on algorithms and data science.
  • Increased part of speech tagger quality from 96% to 97%.
Technologies: Amazon Web Services (AWS), OpenNLP, Keras, TensorFlow, Scikit-learn, Deep Learning, Generative Pre-trained Transformers (GPT), Natural Language Processing (NLP), Data Science, Java, Python

Analyst Engineer (Machine Learning)

2011 - 2013
  • Developed an anti-spam system for an email provider that had tens of millions of users.
  • Created a geo-tracking solution for ads which increased accuracy from 50% to 80%.
  • Implemented Nginx plugin using C with 6000 geo-tracking requests per second per server.
  • Built the back end for email IMAP protocol which enabled 100,000 users to use their favorite email clients.
Technologies: Natural Language Processing (NLP), Generative Pre-trained Transformers (GPT), Machine Learning, Weka, MySQL, C++, Java

AI-powered Writing Assistant

Grammarly is an AI-powered writing assistant. My contribution was creating various error-correction algorithms using data science. For example, a contextual spelling checker, identifying sentences that don't make sense, and complex word identification.
2011 - 2013

Master's Degree in Systems Analysis

National Technical University of Ukraine "Kyiv Polytechnic Institute" - Kyiv, Ukraine

2007 - 2011

Bachelor's Degree in Systems Analysis

National Technical University of Ukraine "Kyiv Polytechnic Institute" - Kyiv, Ukraine


How to Start a Startup

Prometheus, Y Combinator


Intro to TensorFlow for Deep Learning



Scikit-learn, TensorFlow, Standard Template Library (STL), Matplotlib, NumPy, Pandas, OpenNLP, Keras, OpenCV, Natural Language Toolkit (NLTK), SpaCy


Apache OpenNLP, Jupyter, Weka, Rasa.ai, Boto


Python, Java, C++, Bash


Spark, Hadoop, Flask, Boost, Spring


Data Science


Docker, Amazon Web Services (AWS), Azure


MySQL, PostgreSQL, MongoDB


Natural Language Processing (NLP), Algorithms, Machine Learning, Classification Algorithms, Data Analysis, Generative Pre-trained Transformers (GPT), Deep Learning, Data Cleaning, Data Visualization, Time Series, Chatbots

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