SCD in Pipelines

Concepts covered: paScdPipeline

What They Want to Hear 'I implement SCD Type 2 with a MERGE statement that does two things: when a matching row's attributes have changed, it closes the current row by setting end_date and is_current = false, and inserts a new row with the updated values. The surrogate key is a hash of the business key plus the start_date, which makes it deterministic and idempotent.' This is the answer that shows you have built SCD pipelines, not just drawn them on a whiteboard.

About This Interactive Section

This section is part of the Keeping Data Fresh: Intermediate lesson on DataDriven, a free data engineering interview prep platform. Each section includes explanations, worked examples, and hands-on code challenges that execute in real time. SQL queries run against a live PostgreSQL database. Python runs in a sandboxed Docker container. Data modeling problems validate against interactive schema canvases. All content is framed around what data engineering interviewers actually test at companies like Meta, Google, Amazon, Netflix, Stripe, and Databricks.

How DataDriven Lessons Work

DataDriven combines four interview rounds (SQL, Python, Data Modeling, Pipeline Architecture) with adaptive difficulty and spaced repetition. Easy problems get harder as you improve. Weak concepts resurface until you master them. Your readiness score tracks progress across every topic interviewers test. Every lesson section ends with problems you solve by writing and running real code, not by picking multiple-choice answers.