Mateusz Cieślak
Verified Expert in Engineering
Data Engineer and Database Developer
Warsaw, Poland
Toptal member since June 21, 2022
Mateusz is an experienced data engineer with more than 20 projects delivered in areas of data analytics and IT implementations. He is an expert in big data technologies (Hadoop, Python, Apache Spark, Azure) and SQL (T-SQL) and is known for building high-performing ETL/ELT data pipelines. At PwC, Mateusz developed a large volume data mart to profile over 300 million citizens by more than 500 variables and an analytics engine to recommend optimal promotional actions with more than 20,000 products.
Portfolio
Experience
- SQL - 10 years
- Python - 10 years
- Spark - 6 years
- Tableau - 6 years
- Microsoft SQL Server - 6 years
- Hadoop - 6 years
- Azure - 3 years
- Azure Data Factory (ADF) - 3 years
Preferred Environment
Windows, Linux, Visual Studio Code (VS Code), PyCharm
The most amazing...
...project I've delivered was the IFRS9 benchmark testing tool. I served as a developer and an analyst to deliver the app in less than a month.
Work Experience
Senior Data Engineer
ProData Consult
- Developed E2E ETL flows for a client from the banking industry that responsible for the transformation of billions of records. Data was used to train fraud detection models.
- Optimized existing data pipelines, which, in some cases reduced execution time by 95%.
- Set up best practices within the team around MLOps, code quality (all newly developed pipelines having 100% unit test coverage) and data quality.
Senior Data Engineer
PwC Poland
- Developed and maintained a large volume data mart used to profile US citizens. Each citizen (300 million+) was profiled by more than 500 direct features.
- Implemented an IFRS 9 benchmark testing tool to forecast credit stability in terms of repayment for hundreds of thousands of credit exposures.
- Implemented ISO 20000 standard within the Data Analytics team, consisting of more than 100 people.
Data Engineer
PwC Poland
- Developed an analytics engine used to recommend optimal promotional actions for a leading retail store chain in Poland. The engine included more than 20,000 products and gave recommendations based on real client receipt data.
- Created a demand and profitability forecasting tool for a leading food manufacturer in Poland. The utility covered 300 products and gave predictions based on past invoices and terms of contract extracted using text mining algorithms.
- Developed an application handling the sale process of financial assets in accordance with MiFID II. Acted as a full-stack developer and application architect.
Experience
Customer Data Mart
I also oversaw the technical implementation of the data mart's CCPA (California Consumer Privacy Act) procedure.
Fraud Analytics
MiFID II Application
IFRS9 Benchmark Testing Tool
Education
Master's Degree in Finance and Accounting
Warsaw School of Economics - Warsaw
Bachelor's Degree in Finance and Accounting
Warsaw School of Economics - Warsaw
Certifications
ISTQB Certified Tester Foundation Level
ISTQB® - International Software Testing Qualifications Board
ITIL Foundation
AXELOS Global Best Practice
Skills
Libraries/APIs
PySpark, Pandas
Tools
Tableau, Apache Airflow, Apache Impala, PyCharm
Languages
Python, SQL, JavaScript, Java, C#.NET
Frameworks
Spark, Hadoop
Paradigms
ETL, Agile Software Development, Business Intelligence (BI), ITIL
Storage
Microsoft SQL Server, Apache Hive, Data Pipelines, SQL Server Integration Services (SSIS), PostgreSQL, MySQL
Platforms
Azure, Windows, Linux, Databricks, Visual Studio Code (VS Code)
Other
Data Engineering, Data Architecture, Data Visualization, Azure Data Factory (ADF), Apache Cassandra, Quality Assurance (QA), Data Governance, Corporate Finance
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