Topological Sort — Pipeline Dependency Ordering

Topological sort is what happens when your DAG is the sort problem. Given a set of tasks where some depend on others, produce an ordering where every task comes after all its dependencies. This appears directly in DE interviews as 'design a pipeline scheduler' or 'validate this DAG has no cycles and produce an execution order.' Airflow, dbt, and Prefect all use topological sort internally. Kahn's Algorithm — BFS-Based Topological Sort Level-Parallel Execution — Running Independent Tasks Simultaneously