Thomas Ostrowski
Data Engineer Freelance
Lille area · Hybrid
I design reliable and scalable data pipelines to turn your raw data into business value — from ingestion to analytics.
Malt
Book a call What I do
I build and modernize data stacks for organizations that want to take control of their data and industrialize their analytics pipelines.
Technical skills
Types of engagements
Data Architecture
Data lakehouse design, medallion architecture, Data Mesh. Technology choices aligned with your needs.
ETL/ELT Pipelines
Development of robust pipelines with Spark, Airflow and dbt. Batch ingestion and real-time streaming.
Data Warehouse & BI
Dimensional modeling, SQL/dbt transformations, feeding Power BI, Tableau and Qlik dashboards.
Data Quality
Implementation of data quality monitoring, alerting, observability and governance.
Data CI/CD
Automated testing and deployments via GitHub Actions / GitLab CI. Environment management, model versioning and controlled production releases.
Consulting & Training
Coaching your teams, data stack auditing, training in data engineering best practices.
Industry sectors
My career
8 years of diverse experience in complex data environments.
CA Personal Finance & Mobility
Structuring the Data practice during a migration to a Modern Data Stack. Designed a full training curriculum and reference knowledge base to accelerate team upskilling. Industrialized development workflows through GitLab CI templates, a shared dbt foundation project, and the definition of coding and architecture standards.
CA Personal Finance & Mobility
Structuring the Data practice during a migration to a Modern Data Stack. Designed a full training curriculum and reference knowledge base to accelerate team upskilling. Industrialized development workflows through GitLab CI templates, a shared dbt foundation project, and the definition of coding and architecture standards.
Decathlon
Structuring and streamlining the Decathlon Modern Data Stack. Migration of Talend flows to dbt, rationalization of the Tableau dashboard landscape (merging and decommissioning). Building a centralized semantic layer for strategic metrics, prepared for GenAI use cases.
Decathlon
Structuring and streamlining the Decathlon Modern Data Stack. Migration of Talend flows to dbt, rationalization of the Tableau dashboard landscape (merging and decommissioning). Building a centralized semantic layer for strategic metrics, prepared for GenAI use cases.
Decathlon
Complete overhaul of the Decathlon Finance BU analytical stack. Medallion Lakehouse architecture on AWS (S3, Glue), migration of Talend flows to dbt on Databricks, orchestration via Airflow. Migration of dozens of Qlik Sense dashboards to Tableau.
Decathlon
Complete overhaul of the Decathlon Finance BU analytical stack. Medallion Lakehouse architecture on AWS (S3, Glue), migration of Talend flows to dbt on Databricks, orchestration via Airflow. Migration of dozens of Qlik Sense dashboards to Tableau.
Decathlon
Built from scratch e-commerce financial flows across 50+ countries. End-to-end orchestration via OpCon, from Talend extraction through to Qlik Sense reports. Fully industrialized and reliable flows with no manual intervention.
Decathlon
Built from scratch e-commerce financial flows across 50+ countries. End-to-end orchestration via OpCon, from Talend extraction through to Qlik Sense reports. Fully industrialized and reliable flows with no manual intervention.
Decathlon
Migration of several hundred financial reports from Oracle BI to Qlik Sense, covering 50+ countries. Centralization of KPIs in a shared parameter database and deployment automation via the Qlik API.
Decathlon
Migration of several hundred financial reports from Oracle BI to Qlik Sense, covering 50+ countries. Centralization of KPIs in a shared parameter database and deployment automation via the Qlik API.
ACSSI
Data consultant working with multi-sector clients (retail, finance, transport, telecommunications). Delivery of business dashboards in Qlik Sense and QlikView, from requirements gathering to production. Progressive skill development across the entire data chain, up to key missions at Decathlon modernizing their analytical infrastructure.
ACSSI
Data consultant working with multi-sector clients (retail, finance, transport, telecommunications). Delivery of business dashboards in Qlik Sense and QlikView, from requirements gathering to production. Progressive skill development across the entire data chain, up to key missions at Decathlon modernizing their analytical infrastructure.
Tymate
Team development of Android applications for major clients (Decathlon, Europcar). Contribution to key features of Domyos Coach: real-time sports session tracking, integration of a video processing pipeline. Close collaboration with UX/UI teams for polished interfaces.
Tymate
Team development of Android applications for major clients (Decathlon, Europcar). Contribution to key features of Domyos Coach: real-time sports session tracking, integration of a video processing pipeline. Close collaboration with UX/UI teams for polished interfaces.
Tymate
Internal mobile application built from scratch to manage agile sprints on the go. REST API on the server side and Android app development on the client side. Real-time access to velocity indicators without needing a fixed workstation.
Tymate
Internal mobile application built from scratch to manage agile sprints on the go. REST API on the server side and Android app development on the client side. Real-time access to velocity indicators without needing a fixed workstation.
University of Maribor
Android application built from scratch for an international academic conference. Intuitive navigation, content embedded in a local database for offline access. First project delivered in full autonomy, from design to launch.
University of Maribor
Android application built from scratch for an international academic conference. Intuitive navigation, content embedded in a local database for offline access. First project delivered in full autonomy, from design to launch.
What they say
Authentic client feedback from the projects I have led.
"I worked with Thomas for 6 years within our finance data team. Beyond his expertise, he is a partner who knows how to challenge technical decisions and best practices to ensure alignment between data and business needs. His constructive directness and ability to step back are real assets for successfully delivering complex projects.
"J'ai collaboré avec Thomas pendant 6 ans au sein de notre équipe finance data. Au-delà de son expertise, c'est un partenaire qui sait challenger les décisions techniques et les best practices pour garantir une cohérence entre la data et les besoins métiers. Sa franchise constructive et sa prise de recul sont de vrais atouts pour mener à bien des projets complexes.
Want to find out more? Check my recommendations on Malt and LinkedIn.
Let's talk about your project
A project, a question, an opportunity? I will reply within 24 hours.
Information
⚡ Response within 24 business hours
Message sent!
Thank you for your message. I will get back to you as soon as possible.