Technical Lead — Data Science (f/m/x)

Sii Poland; Kraków; On-site; PLN 300,000 - 420,000; Full time

Benefits offered by this job

Great Place to Work

Financial stability

Brand contracts

Internal trainings

Mentor network

Open management

Profit sharing

Sponsorship program

Team events

Modern offices

MySii app

Medical care

Job summary

Sii Poland is seeking a technical lead for data science who can steer end-to-end engagements from framing problems to sign-off on modeling approaches. The role combines hands-on Python work with leadership, standards setting, and client-facing delivery across major cloud and data platforms.

You will mentor a team of data scientists, review methodology, and ensure reproducible, production-grade outcomes while collaborating with AI architects and engineers.

Qualifications

• 6+ years in data science with production models.
• Minimum 2 years leading or mentoring data scientists.
• Hands-on Python plus core data stack (pandas, NumPy, scikit-learn, XGBoost).
• Cloud/data platform experience: Azure, AWS, or GCP; Snowflake/Databricks/Foundry familiarity.
• Strong communication, able to defend methods to technical and non-technical audiences.
• Fluent English and Polish; residing in Poland.

Responsibilities

• Own the technical direction of data science engagements: solution design, modeling approach, validation strategy, and delivery quality.
• Lead and mentor a team of data scientists — code reviews, methodology reviews, career development.
• Stay hands-on: prototype approaches and contribute production-grade Python where it matters.
• Translate client business problems into scoped, estimable data science workstreams.
• Set and enforce engineering standards: reproducibility, experiment tracking, testing, documentation.
• Guide platform decisions across cloud/data ecosystems (Fabric, Foundry, Databricks, Snowflake, Azure/AWS/GCP).
• Collaborate with AI Architects, data engineers, and client stakeholders to align tech with business outcomes.
• Represent the team to clients: present results and defend methodology.

Skills

6+ years data science

2+ years leadership

Python

Pandas

NumPy

scikit-learn

XGBoost

Cloud platforms

Communication

Fluent English

Fluent Polish

Poland resident

Tools

Azure

AWS

GCP

Databricks

Snowflake

Palantir Foundry

Microsoft Fabric

Job description

We’re looking for a technical lead who can do two hard things at once: keep a team of data scientists shipping work that holds up to scrutiny, and stay close enough to the code to know when it doesn't. You’ll own the technical direction of data science projects end-to-end — from framing the problem with the client to signing off on the modeling approach, reviewing the work, and making sure what gets delivered actually runs.

This is a hands-on role. You’ll still write Python, still challenge model choices, still dig into why the metrics look too good. But your biggest impact will come through others — setting standards, mentoring the team, and making the technical calls that keep projects on track across platforms like Microsoft Fabric, Palantir Foundry, Databricks, and the major clouds.

What We Offer

AI Grant — Stop talking about AI and start building it. Our AI Grant gives you dedicated budget and resources to turn your wildest AI idea into a working project, backed by two paid weeks to focus on nothing else.

AI Center of Excellence — Work alongside specialists in agentic AI, sovereign AI, generative and discriminative AI. This isn’t a siloed team — it’s the people you’ll learn from and build with daily.

Your tools, your choice — Full access to AI-powered development tools including Claude, Cursor, and GitHub Copilot. Pick what works best for you.

Real project variety — From generative AI for legal document compliance, through agentic systems in manufacturing environments, to enterprise-scale AI platforms, computer vision, and autonomous driving. You won’t get bored.

Conference and speaking support — Want to attend conferences? We’ll back you. Want to speak at them? Even better — we’ll support you with dedicated preparation time and bonuses.

Your tasks

• Own the technical direction of data science engagements: solution design, modeling approach, validation strategy, and delivery quality
• Lead and mentor a team of data scientists — code reviews, methodology reviews, career development, and raising the bar on what "done" means
• Stay hands-on: prototype approaches, unblock the team on hard modeling problems, and contribute production-grade Python where it matters most
• Translate client business problems into scoped, estimable data science workstreams, and push back when the problem doesn’t need a model
• Set and enforce engineering standards for the team: reproducibility, experiment tracking, testing, and documentation
• Guide platform decisions and delivery across cloud/data ecosystems — Microsoft Fabric, Palantir Foundry, Databricks, Snowflake, and native Azure/AWS/GCP services
• Work with AI Architects, data engineers, and client stakeholders to align technical decisions with business outcomes and timelines
• Represent the team in front of clients: present results, defend methodology, and manage technical expectations

Requirements

• At least 6 years in data science with a track record of models shipped to production, including a minimum of 2 years leading or mentoring other data scientists
• Deep, hands-on Python skills across the standard data stack (pandas, NumPy, scikit-learn, XGBoost) — you can still review and write the hard parts yourself
• Strong statistical and ML foundations: experimental design, validation methodology, and the judgment to spot results that won’t survive contact with reality
• Familiarity with at least one cloud/data platform and its data science components — Azure (Microsoft Fabric, Azure Machine Learning), AWS (SageMaker), GCP (Vertex AI, BigQuery ML), Snowflake (Snowpark ML, Cortex), Databricks (MLflow, Mosaic AI), or Palantir (Foundry Code Workspaces, Foundry ML, AIP)
• Experience leading delivery in a client-facing or consulting context: scoping, estimation, and managing technical risk
• Strong communication skills — able to defend a methodology to a technical audience and explain its business impact to a non-technical one
• Fluent English (both written and spoken)
• Fluent Polish required
• Residing in Poland required

Nice to have

• Production experience with Microsoft Fabric or Palantir Foundry, or relevant platform certifications
• Experience with MLOps at team scale: CI/CD for ML, model registries, monitoring, and governance
• Exposure to GenAI/LLM projects and judgment about where they do — and don’t — belong in a data science solution
• Public technical presence: conference talks, publications, or open-source contributions

Job no. JOB-GWX76

Sii ensures that all hiring decisions are made solely on the basis of qualifications and competence. We are committed to equal and fair treatment of all, regardless of legally protected characteristics. At Sii, we promote a diverse and inclusive work environment, in full compliance with applicable anti-discrimination laws.

Benefits For You

• Great Place to Work
• Solid financial situation
• Contracts with the biggest brands
• Centre of internal trainings
• Many experts you can learn from
• Open and accessible management team
• Profit sharing
• Passion Sponsorship program
• Regular integration events and trips
• Comfortable and well-equipped offices
• MySii app
• Medical care