PDE Ingesting and Processing the Data Practice Question
A company is using Pub/Sub to ingest clickstream events and Dataflow to write to BigQuery. They observe that some events are malformed and cause the pipeline to fail. They need a solution that captures malformed events without blocking the pipeline and allows reprocessing later. Which Dataflow pattern should they implement?
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
✓
Write malformed events to a dead letter sink (e.g., another Pub/Sub topic or GCS bucket) and continue processing healthy events
Dead letter sinks (DLQ) are the standard pattern for handling bad records in Dataflow. The pipeline writes malformed records to a separate sink (e.g., Pub/Sub topic or GCS) for later analysis. Side inputs are for enriching data, not error handling. Reshuffle doesn't apply. Output tags (side outputs) can also be used, but explicit dead letter pattern is more standard.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use a side input to filter malformed events before the main pipeline
Why it's wrong here
Side inputs are for joining additional data, not error handling.
- ✗
Use the Reshuffle transform to reattempt failures
Why it's wrong here
Reshuffle is used to repartition data, not for error handling.
- ✓
Write malformed events to a dead letter sink (e.g., another Pub/Sub topic or GCS bucket) and continue processing healthy events
Why this is correct
Dead letter sink is the correct pattern: isolate bad records and let the pipeline proceed.
- ✗
Use logging alerts to notify the team and stop the pipeline on error
Why it's wrong here
Stopping the pipeline on error is not desired; the team wants to continue processing.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.