Cron expressions in Airflow - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a cron expression in Airflow?

A cron expression in Airflow is a string that defines the schedule for running a task. It uses five fields to specify minute, hour, day of month, month, and day of week.

beginner

What does the cron expression '0 12 * * *' mean in Airflow?

It means the task runs every day at 12:00 PM (noon). The fields are: minute=0, hour=12, day of month=any, month=any, day of week=any.

intermediate

How do you schedule a task to run every Monday at 8 AM using a cron expression in Airflow?

Use the cron expression '0 8 * * 1'. This means minute=0, hour=8, any day of month, any month, and day of week=1 (Monday).

beginner

What does the '*' symbol mean in a cron expression?

The '*' symbol means 'every' possible value for that field. For example, '*' in the month field means every month.

intermediate

How can you run a task every 15 minutes using a cron expression in Airflow?

Use '*/15 * * * *'. The '*/15' in the minute field means every 15 minutes, and the other fields are set to run every hour, day, month, and day of week.

What does the cron expression '30 6 * * *' schedule in Airflow?

A Runs at 6:30 AM every day

B Runs at 6:00 AM every 30 days

C Runs every 30 minutes starting at 6 AM

D Runs at 6:30 PM every day

The first field is minutes (30), second is hour (6), so it runs at 6:30 AM daily.

Which cron expression runs a task every Sunday at midnight in Airflow?

A 0 0 * * 0

B 0 0 * * 7

C 0 0 * * 1

D 0 0 7 * *

In cron, Sunday can be 0 or 7. '0 0 * * 0' and '0 0 * * 7' both mean midnight on Sunday.

What does the cron expression '15 14 1 * *' do in Airflow?

A Runs every day at 2:15 PM

B Runs at 1:14 PM every day

C Runs every 15 minutes starting at 2 PM

D Runs at 2:15 PM on the first day of every month

Minute=15, hour=14 (2 PM), day of month=1 means first day of each month at 2:15 PM.

How do you express 'every hour' in a cron expression for Airflow?

A * * * * *

B * 0 * * *

C 0 * * * *

D 0 0 * * *

"0 * * * *" means at minute 0 of every hour, every day.

Which part of the cron expression controls the day of the week in Airflow?

A Fifth field

B Second field

C First field

D Third field

The fifth field in a cron expression is for the day of the week (0-6 or SUN-SAT).

Explain how to read a cron expression in Airflow and give an example.

Think of each field as a time unit that controls when the task runs.

Describe how to schedule a task to run every weekday at 9 AM using a cron expression in Airflow.

Weekdays are Monday to Friday, which are days 1 to 5.