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Data Science Lead

Data Science Lead

Type of work
Employment Type
Operating mode

Tech stack

    Data Science

Job description


We're Castle, a profitable Series A startup on a quest to redefine trust and safety for users across large consumer platforms like Canva, Atlassian, and Rockstar Games. We're backed by Y Combinator, Index Ventures, as well as prominent angel investors from Datadog, Stripe, and New Relic.

As our Lead Data Scientist, you will be entrusted with steering our pioneering efforts in anti-fraud research. Collaborating directly with our CTO and integrated within our Product Team, you will have an incredible amount of impact on the direction and implementation of our projects and the product. This position calls for a leader who can refine our research methodologies, expand our data science frontier, and help us grow our Data Science team.

This hybrid role requires your presence two days a week at our Krakow office. Your teammates are based in the US, Poland, Portugal, and Sweden.


  • Collaborate with our CTO to understand and validate new concepts, turning them into tangible PoCs.
  • Lead the development and optimization of data collection, collaborating closely with the Engineering Team team to design, build PoC, refine, and integrate these algorithms using Python, Ruby, and JavaScript into Snowflake UDFs and production environments.
  • Drive the strategic direction for enhancing our capabilities in fingerprinting, bot detection, and risk assessment, while closely monitoring and improving key performance indicators such as fingerprint accuracy and collision rates.
  • Collaborate with our customers to translate feedback into actionable data science initiatives, enriching our anti-fraud research and product evolution.
  • Employ creativity to overcome challenges in unlabeled data, pioneering unconventional labeling strategies and proxies to refine our models.
  • Proactively formulate new research ideas, demonstrating self-sufficiency and a keen investigative spirit to advance our data science endeavors.


  • A startup mindset – flexibility, agility, and adaptability - we are passionate about limiting work-in-progress and deeply value work/life balance, but this is a startup, and you will be expected to pivot between projects/codebases/areas of work regularly.
  • MSc in Computer Science, Data Science, or related (Bachelor's with exceptional experience acceptable).
  • 5+ yrs of experience in a Data Science role, ideally within a startup or agile tech company.
  • 3+ yrs of programming, preferably in Python, Ruby, JavaScript, or similar.
  • Proficient in using Python & Pandas to build models and develop PoCs.
  • Proven expertise in Data Science with a focus on product innovation in a tech-driven environment.
  • Experience with OLAP databases (we are using Snowflake)
  • Demonstrated experience in managing and analyzing large datasets with an eye for detail and accuracy.
  • Leadership experience in fast-paced startups.
  • Strong analytical and problem-solving prowess

Our benefits

  • Stock option program.
  • Flexible work hours. We prioritize outcomes over hours spent.
  • Unlimited paid PTO. Take the time you need to recharge and maintain a healthy work-life balance.
  • Paid sick leaves
  • Paid parental leave
  • We'll provide the essential computer and related equipment to ensure you have everything you need to excel in your role
  • Company off-sites and team activities.