Task Dependencies

Concepts covered: paDependencyMgmt

What They Want to Hear 'Within a DAG, dependencies are edges: Task A runs before Task B. Across DAGs, it gets harder. Sensors poll for a signal (a file exists, a partition is populated). Event triggers fire when data is ready (Airflow datasets since v2.4). The tradeoff: sensors waste compute by polling, event triggers are more efficient but require the producer to publish a signal.'

About This Interactive Section

This section is part of the Making It Repeatable: Beginner 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.