Job Opportunities in the Daphni Portfolio


Senior Data Scientist | Ranking



Data Science
Poland · Remote
Posted on Friday, June 28, 2024
At OLX, we work together to build a more sustainable world through trade.
We make it safe, smart, and convenient to buy and sell cars, find housing, get jobs, buy and sell household goods, and more. Our colleagues around the world help to serve millions of people around the world every month, through its well-loved consumer brands including OLX, Otodom, Property24.
Join OLX and see how far you can go.
Data Science org
The Data Science team at OLX Group is responsible for building algorithmic solutions to facilitate transactions between buyers and sellers. We are developing personalization technologies and optimization strategies that have a direct impact on OLX’s users as well as the company’s bottom line.
You will be encouraged to research state-of-the-art machine learning, in the areas of search relevance, ranking, recommender systems, and more. Applying these methods to core OLX product platforms deployed in the cloud that are affecting the user experience for millions of visitors per month, rolling your solutions to production, analyzing model results offline and online, and measuring site impact.
Some of the challenges that we are focusing on are maximizing the relevance of the search results by applying ML-based rankers, combining different sources of ads in search and recommendations to optimize the satisfaction of both buyers and sellers, estimating the impact that the interactions generated by the buyers have on the revenue, and detecting trending products even before they become popular.
The Ranking Data Science team
The Ranking Data Science team at OLX Group is responsible for building and scaling ranking algorithms across OLX Europe. Our main goal is to help our stakeholders to increase efficiency and performance by delivering state-of-the-art LTR algorithms across our platform to serve our customers when looking for items in our vast catalog. In a nutshell, you will be exposed to projects such as: Multiobjective optimization (e.g., optimize for more than one revenue stream), Personalisation (user personalization), LTR Framework (ability to train models capable of optimizing specific targets based on varying contexts within OLX’s sectors like Motors and Real Estate), or Semantic Search (Integration and optimization of the end-to-end search flow).
Our team collaborates with product and tech teams from OLX, as well as the Motors and Real Estate verticals like Otomoto and Otodom, across the entire EU region. This means that our solutions need to scale to millions of data points and need to be designed to be reused in markets with similar characteristics. We think of experimentation as a tool to learn what our users want. We always start simple and fail fast. This way we can create solutions that can be adapted to every market.
On a typical day, you will be interacting with other members of your cross-functional team. You may collaborate with a data analyst to analyze the results of an A/B test or discuss different alternatives to impact the team’s KPIs with the product manager, or you may have to present your amazing Jupyter notebook to other data scientists to collect feedback. In any case, you will find a group of friendly people who want to collaborate with you to improve our platform capabilities and the user experience and ultimately have fun together!

What you will be doing:

  • Work in multi-functional teams with people from different backgrounds to build our Recommendations Platform
  • Find opportunities where data science will make an impact
  • Help to translate business requirements into machine learning models
  • Build effective solutions with machine learning
  • Bring machine learning services to production together with engineers
  • Measure the impact of your models on company goals
  • Collaborate with internal and external stakeholders

Your skills and experience:

  • Experience with Learning-to-Rank
  • Strong data analysis and machine learning skills
  • At least 5 years of professional data science experience
  • Experience participating in projects related to search relevance and ranking
  • Strong engineering background: proficiency in Python and a good understanding of best engineering practices
  • Exposure to other programming languages such as Kotlin, Java, Scala, etc
  • Experience with at least two of the following machine learning frameworks: Scikit-Learn, XGBoost, TensorFlow, PyTorch, (or similar)
  • Hands-on experience in the Python ecosystem for data science
  • Understanding of A/B testing and experimentation
  • Proficient in English with excellent written and oral communication skills

Nice to have:

  • Experience bringing models into production and serving models at scale
  • Experience using AWS for deploying machine learning solutions
  • Experience with building data pipelines using tools like Spark and Airflow
  • Experience with Solr or Elasticsearch
  • Exposure to NLP libraries such as spaCy, SparkNLP or BERT
  • Exposure to production infrastructure and DevOps practices: monitoring, alerting, CI/CD, container-orchestrating platforms, and infrastructure-as-code tools (Grafana, Prometheus, Kubernetes, Terraform)
  • Exposure to MLOps tools

What we offer:

  • Contract of employment (not B2B!).
  • Competitive salary + annual bonus up to 15% of your annual gross salary.
  • Intellectual Property tax deductible costs are applicable up to 70% of the base salary.
  • MyBenefit platform package with 300 points monthly credit, private medical care (PZU Zdrowie), Ask Henry services, and more.
  • 100% remote work and the possibility to work from our offices in Poznan and Warsaw.
  • Training and conference budget + free access to O'Reilly, Udemy courses, and more.
  • A passionate and diverse team of data scientists spanning across several tech hubs in Europe.
Why join OLX?
At OLX, we invest in ourselves and each other to reach our full potential. We avoid bureaucracy and empower our teams to innovate; with opportunities, training, and leadership behaviors a key focus for all. Our commitment to inclusion ensures we listen to a diverse range of voices when making decisions. And, we combine the spirit and agility of a startup with our global scale and the backing of Prosus, one of the largest consumer internet groups in the world.
Diversity, Equity and Inclusion at OLX
At OLX, we are committed to creating a diverse, inclusive, and authentic workplace. We strongly encourage people of all races, ethnicities, disabilities, ages, gender identities or expressions, sexual orientations, religions, backgrounds, and experiences to apply.
If you are excited about this role, and your past experiences do not align perfectly with every criteria asked for in the job description, we would still like you to apply. You may be just the right candidate for this or other opportunities across the business, and we'd like to hear from you.
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