PDE Designing Data Processing Systems Practice Question
A company is using Pub/Sub to ingest clickstream events. They need to ensure that events are delivered to a subscriber at least once, but duplicates can be tolerated. They also need to filter events by type before processing. Which subscription configuration should be used?
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
✓
Pull subscription with a filter on event type attribute
Pub/Sub provides at-least-once delivery for both pull and push subscriptions. Filtering by attributes is supported at subscription level. Pull subscriptions are typically used when the subscriber controls the pace. Push subscriptions are also possible, but the question does not specify delivery method preference. The key is to enable message filtering on the subscription.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Pull subscription with exactly-once delivery enabled
Why it's wrong here
Exactly-once delivery is available but not required; the question says duplicates are tolerated. Enabling it may add overhead and is unnecessary.
- ✗
Push subscription with no filter
Why it's wrong here
Push subscriptions deliver all messages; no filtering is applied unless specified.
- ✓
Pull subscription with a filter on event type attribute
Why this is correct
Pull subscriptions allow the subscriber to control message flow. Filtering on attributes ensures only matching messages are delivered. At-least-once is default.
- ✗
Push subscription with a dead letter topic
Why it's wrong here
Dead letter topics handle undeliverable messages, not filtering.
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Senior Network & Security Engineer · founder of Courseiva
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