Data Engineering Tech Lead

Cosmose, Inc.; Warszawa; On-site; PLN 280,000 - 420,000; Full time

Job summary

Cosmose AI in Warsaw is seeking a hands-on Data Engineering Tech Lead to own the data platform and lead a small team of Data Engineers. You will set technical direction, stay deep in code, and drive end-to-end initiatives with a focus on scalable data architectures.

The role requires strong Python/Java experience, deep knowledge of distributed systems, and a track record of building robust data pipelines and data models.

Qualifications

• Strong software engineering background with production experience in Python or Java.
• Deep understanding of distributed systems and data processing across multiple systems.
• Strong data engineering experience — pipelines, data platforms, warehouses/lakes and data modeling.
• Ability to make architectural decisions independently and reason about long-term impact.
• A strong sense of ownership and proactive problem discovery.
• High standards for performance, reliability, cost, data quality and engineering discipline.

Responsibilities

• Own the technical direction of the data platform and make architectural decisions.
• Stay hands-on—design systems, write production code, review implementations, and solve hard problems.
• Drive end-to-end initiatives from discovery to production release.
• Optimize performance and cost across data models, storage, processing, and queries.
• Define data contracts, schemas, ownership, documentation, standards, and quality practices.

Skills

Python

Java

Distributed systems

Data engineering

Architectural decisions

Ownership

Performance optimization

Data contracts

Tools

Flink

ClickHouse

Iceberg

Spark

SQL

Job description

About Cosmose AI

We make smartphones smarter. Cosmose is integrated by eight phone makers, capturing first-screen real estate and first-party data to drive over 2 billion daily user interactions in 60+ countries.

About Cosmose AI

We make smartphones smarter. Cosmose is integrated by eight phone makers, capturing first-screen real estate and first-party data to drive over 2 billion daily user interactions in 60+ countries.

Why Join Cosmose AI

• Global Scale: Build a product natively integrated across eight major OEMs with access to first party data from millions of phones in over 60 countries.
• Elite Talent Density: Work alongside IOI and ACM-ICPC champions.
• High Autonomy, Fast Velocity: Take complete ownership with rapid deployment cycles and a flat org chart.
• Real Ownership: Earn stock options that directly tie your upside to our global growth and success.

We're looking for a hands-on Data Engineering Tech Lead to own the technical direction of our data platform and lead a small team of Data Engineers.

This is a dual role: you'll set technical direction and stay deep in the code, while also leading the team day-to-day - 1:1s, mentorship, technical growth and hiring.

What You'll Do

• Own the technical direction of our data platform and make architectural decisions with a clear grasp of their trade-offs and long-term consequences.
• Stay hands-on - design systems, write production code, review implementations and solve the hardest problems yourself.
• Drive initiatives end-to-end - identify important problems on your own, propose solutions and see them through to production.
• Optimize for performance and cost across the platform, from data models and storage to processing and querying.
• Build order in Data - establish clear data contracts, schemas, ownership, documentation, standards and quality practices. You'll also own the data interfaces other teams depend on.
• Solve distributed systems problems - consistency, exactly-once processing, fault tolerance, schema evolution, streaming, storage, scalability and performance.
• Lead and grow the team - through technical direction, reviews, mentorship and regular 1:1s.

What We're Looking For

• Strong software engineering background with production experience in Python or Java.
• Deep understanding of distributed systems and the problems that arise when data is processed and stored across multiple systems.
• Strong data engineering experience - pipelines, data platforms, warehouses/lakes and data modeling.
• Ability to make architectural decisions independently and reason about their long-term impact.
• A strong sense of ownership - you find problems and opportunities yourself rather than waiting for a backlog.
• High standards for performance, reliability, cost, data quality and engineering discipline.Clear communication of technical decisions and effective work across teams (Polish and English are required)
• Ability to learn new technologies quickly and reason about unfamiliar systems.

Our stack

• Flink, ClickHouse, Iceberg, Spark, Python and Java.
• You don't need experience with all of them - we care more about strong fundamentals and your ability to pick up new technologies and apply them well.

What Success Looks Like

• The team has clear technical direction and ownership.
• The platform is reliable, performant, scalable and cost-efficient.
• Data contracts, schemas, ownership and documentation are well defined.
• Technical debt and systemic problems are actively surfaced and addressed.
• Data consumers trust the platform and rely on it in their day-to-day work.

We're building something big and we're just getting started.

If you're excited about shaping the future of AI-powered mobile content, we'd love to meet you.

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