Key Generation Strategies

Concepts covered: dmKeyGeneration, dmSurrogateKeys

How you generate surrogate keys has real implications for performance, correctness, and pipeline complexity. There are three main strategies: database sequences, hash-based keys, and UUIDs. Each fits different scenarios. Database Sequences A sequence is a database-maintained counter that increments atomically. Each call to NEXTVAL returns a unique integer. Sequences are fast and produce compact, ordered values that B-tree indexes love. The downside: in distributed insert pipelines (e.g., Spark writing to PostgreSQL), every executor contends for the same sequence, creating a bottleneck. Hash-Based Keys A hash-based surrogate key applies a deterministic hash (MD5, SHA-256) to one or more business attributes. The same input always produces the same output. This is what makes hash keys powerfu

About This Interactive Section

This section is part of the Keys & Identity 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.

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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.