DevOps · Flashcard
Which Pub/Sub subscription types support exactly-once delivery?
- APull subscriptions only — push and export subscriptions do not support it
- BPush subscriptions only — pull and export subscriptions do not support it
- CPull and push subscriptions — only export subscriptions are excluded from it
- DEvery subscription type — provided the topic has message ordering switched on
Why this is the answer
Exactly-once delivery is available on pull subscriptions only; push and export subscriptions do not support it. The reversed answer is the tempting one because push feels more controlled, but the guarantee depends on the acknowledgement handshake a pull client performs. Including push is therefore wrong, and message ordering is an independent feature that does not unlock exactly-once anywhere.
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