Denys Kulemza

I am a senior data engineer building an independent data platform consultancy from Spain. I build and optimize scalable data pipelines, with a deep focus on Databricks and Apache Spark.

Day to day I debug query plans, fix skew and shuffle pathologies, kill expensive UDFs, and design the boring patterns that survive the next platform migration. I have led migrations off CDH, Teradata, and Hadoop onto Snowflake and Databricks.

I write about what actually breaks in production, not theory. Skew, cache misuse, Delta and Iceberg cleanup, retention, UDF cost. The same problems I get hired to fix.

I sell data engineering for real outcomes. Clean, production-grade pipelines are what let a company actually ship analytics and AI features. The pipeline and the data quality are the work.