Apache Airflow Fundamentals · 20% of the exam
5 sample questions from our 13-question bank for this domain — answers and explanations included. These are the same scenario-based style as the real Astronomer exam.
1. What is an OPERATOR in Airflow?
An operator is a predefined template for a unit of work (e.g., run Bash, run Python, transfer data); when you instantiate an operator in a DAG, you create a task. It's not the scheduler (B), a connection (C), or the UI (D).
2. Which operator is a no-op placeholder often used to group tasks or mark start/end points in a DAG?
The EmptyOperator (previously DummyOperator) does nothing and is used to structure a DAG — grouping branches or marking start/join/end points. The PythonOperator (B) and BashOperator (C) do real work, and S3KeySensor (D) waits for an S3 object.
3. What are XComs used for in Airflow?
XComs (cross-communications) let tasks push and pull small pieces of data (like an ID or a value) to share between them. They are NOT meant for large data (B) — use external storage for that; they don't define schedules (C) or render the UI (D).
4. What is a SENSOR in Airflow?
A sensor is an operator that waits (polls) until a condition is true — a file exists, a partition lands, a time is reached — then allows downstream tasks to proceed. It's not a dashboard (B), index (C), or executor (D).
5. Which operator runs a shell command as a task?
The BashOperator executes a Bash/shell command. The PythonOperator (B) runs Python callables, SqlSensor (C) waits for a SQL condition, and EmptyOperator (D) is a no-op placeholder.
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