A subscription uses the default message retention period. A consumer team was away for eight days and never acknowledged the messages that arrived during that time. What happens to those unacknowledged messages?
Show answer and explanation
Answer: C
Message retention on a subscription keeps unacknowledged messages available for delivery for a set period, which is seven days by default and can be extended up to 31 days. Once that period passes, Pub/Sub discards any message that was never acknowledged, so the backlog no longer contains it. A dead-letter topic is not triggered by retention expiry and must be configured separately based on delivery attempts. Pub/Sub never acknowledges messages on a consumer's behalf.
Why the other options are wrong
- A. Pub/Sub never acknowledges messages on a consumer's behalf. Expired messages are removed rather than marked as processed, so the team would not see them as completed.
- B. Pub/Sub does not hold unacknowledged messages forever under default settings. Retention is bounded, so backlog messages are removed after the configured period expires.
- D. Dead-letter topics are triggered by repeated failed delivery attempts when configured. Retention expiry alone does not route messages there, so this outcome is not automatic.