- A
Sensors (e.g., GCSObjectExistenceSensor)
Sensors poll for conditions like file existence.
- B
XComs to pass file path between tasks
XComs allow the sensor to push the file path for downstream tasks.
- C
Operators (e.g., PythonOperator)
Why wrong: Operators perform actions; sensors are a type of operator but specifically for waiting.
- D
SubDAGs for grouping tasks
Why wrong: SubDAGs are optional and not essential for this pattern.
- E
Task dependencies (bitshift operators)
Dependencies ensure ordering: sensor first, then downstream tasks.
Question 351 of 1,000
PDE Maintaining and Automating Data Workloads Practice Question
This PDE practice question tests your understanding of maintaining and automating data workloads. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company uses Cloud Composer (Airflow) to orchestrate pipelines. They want to implement a pattern where a task polls for a file arrival in Cloud Storage and then triggers subsequent tasks. Which THREE Airflow concepts are essential? (Choose 3)
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Sensors (e.g., GCSObjectExistenceSensor)
A is correct because Sensors are a specialized type of operator designed to wait for a specific condition, such as file arrival in Cloud Storage. The `GCSObjectExistenceSensor` in Cloud Composer (Airflow) polls Google Cloud Storage at a configurable interval until the target file exists, making it the precise tool for this file-arrival polling pattern.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Sensors (e.g., GCSObjectExistenceSensor)
Why this is correct
Sensors poll for conditions like file existence.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
XComs to pass file path between tasks
Why this is correct
XComs allow the sensor to push the file path for downstream tasks.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Operators (e.g., PythonOperator)
Why it's wrong here
Operators perform actions; sensors are a type of operator but specifically for waiting.
- ✗
SubDAGs for grouping tasks
Why it's wrong here
SubDAGs are optional and not essential for this pattern.
- ✓
Task dependencies (bitshift operators)
Why this is correct
Dependencies ensure ordering: sensor first, then downstream tasks.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests whether candidates confuse general-purpose Operators (like PythonOperator) with Sensors, leading them to pick Operators for polling tasks when Sensors are the correct, purpose-built solution.
Detailed technical explanation
How to think about this question
Under the hood, Airflow Sensors implement a `poke` method that runs repeatedly at a `poke_interval` (default 60 seconds) until the condition is met or a `timeout` is reached. The `GCSObjectExistenceSensor` uses the Google Cloud Storage client library to call `bucket.blob(file_path).exists()` on each poke, and it can be configured with `mode='reschedule'` to release the worker slot between pokes, improving resource utilization in high-concurrency environments.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this PDE question test?
Maintaining and Automating Data Workloads — This question tests Maintaining and Automating Data Workloads — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Sensors (e.g., GCSObjectExistenceSensor) — A is correct because Sensors are a specialized type of operator designed to wait for a specific condition, such as file arrival in Cloud Storage. The `GCSObjectExistenceSensor` in Cloud Composer (Airflow) polls Google Cloud Storage at a configurable interval until the target file exists, making it the precise tool for this file-arrival polling pattern.
What should I do if I get this PDE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jul 4, 2026
This PDE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PDE exam.
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