Aymen Jaffry, Developer in Paris, France
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Aymen Jaffry

Verified Expert  in Engineering

Machine Learning Developer

Paris, France
Toptal Member Since
September 26, 2018

Aymen has worked for 6+ years as a data scientist, machine learning engineer, and consultant. He has worked in many industries, including finance, advertising, and online marketplaces. He greatly enjoys using machine learning and statistics to build state-of-the-art and efficient solutions. He holds an M.S. in computational engineering from Harvard University and a master's degree in applied/theoretical mathematics from Ecole Centrale Paris.


Models, Reinforcement Learning, Scikit-learn, SQL, Java, Python
Models, Reinforcement Learning, Scikit-learn, SQL, Java, Python
Catalant Technologies
Graph Theory, Recommendation Systems, SQL, R, Python




Preferred Environment

Git, Atom, Jupyter, Python, OS X

The most amazing...

...thing I've built is a system using machine learning and statistics to predict 911 calls at the street level in the Boston area.

Work Experience

Machine Learning Consultant

2016 - 2018
  • Developed an innovative classification algorithm, using online learning, to predict the advertisers’ conversion rates and automate bidding strategies.
Technologies: Models, Reinforcement Learning, Scikit-learn, SQL, Java, Python

Data Scientist, Ad Serving Team

2014 - 2016
  • Worked on display advertising, applying machine learning and reinforcement learning techniques to the problem of predicting click-through-rate.
  • Implemented a dynamic A/B testing platform that allowed thousands of A/B tests to run in parallel.
  • Used Bayesian Statistics and Thompson Sampling to redesign second-price auction rules and A/B testing decisioning.
Technologies: Models, Reinforcement Learning, Scikit-learn, SQL, Java, Python

Machine Learning Consultant

2013 - 2014
Catalant Technologies
  • Built the first version of the matching engine from scratch using graph theory. This system recommends newly posted projects to MBA students on the platform and vice-versa.
  • Ran market analysis to identify lags between offer (projects) and demand (MBA students' expertises).
Technologies: Graph Theory, Recommendation Systems, SQL, R, Python

Consultant in the Statistical Learning Team

2011 - 2012
  • Developed a system in R recommending the best marketing means to reach each new customer on the website.
  • Conducted analysis to build customer groups using unsupervised and supervised learning techniques.
Technologies: Clustering, Principal Component Analysis (PCA), Unsupervised Learning, Scikit-learn, Python, R

Assistant Trader and Structurer

2010 - 2011
UBS Investment Bank
  • Built a prototype tool that dynamically rebuilt a collateral portfolio using the risk of default analysis.
  • Assisted the secured funding team in creating new products by running forecast tests and coming up with.
  • Completed ROI and value propositions.
  • Priced primary/secondary quotes and hedged currency strategies.
Technologies: Time Series Analysis, Visual Basic for Applications (VBA), R

Assistant Researcher

2010 - 2010
Cornell University, CFEM
  • Implemented a multi-agent system based on Ask/Bid and PnL data analysis simulating a stable financial market.
  • Worked under the supervision of Dr. Sasha Stoikov, Head of Research at CFEM.
Technologies: Reinforcement Learning, C++, Java


SQL, Python, Java, R, Visual Basic for Applications (VBA), C++, J


Scikit-learn, Pandas, Matplotlib, Spark ML, TensorFlow, Keras, REST APIs


Jupyter, IPython, Git, Apache Airflow, Atom


Data Science, Object-oriented Programming (OOP)


Eclipse, MacOS, Linux, Docker, OS X

Industry Expertise



MySQL, Amazon S3 (AWS S3)


A/B Testing, Mathematics, Analytics, Big Data, Bayesian Statistics, Advertising, Machine Learning, Vowpal Wabbit, Google BigQuery, Unsupervised Learning, Deep Learning, Natural Language Processing (NLP), Reinforcement Learning, Finance, GPT, Generative Pre-trained Transformers (GPT), Models, Recommendation Systems, Graph Theory, Principal Component Analysis (PCA), Clustering, Time Series Analysis


Apache Spark

2013 - 2014

Master of Science Degree in Computational Science and Engineering

Harvard University - Massachusetts

2009 - 2013

Master's Degree in Applied and Theoretical Mathematics

Ecole Centrale Paris - Paris, France

2006 - 2009

Bachelor of Science Degree in Mathematics, Physics

Marcelin Berthelot Preparatory Classes - Paris, France

Collaboration That Works

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