You have designed an Apache Beam processing pipeline that reads from a Pub/Sub topic. The topic has a message retention duration of one day, and writes to a Cloud Storage bucket. You need to select…

Question

Options

• A
  1. Use a dual-region Cloud Storage bucket.
• C
  1. Use a regional Cloud Storage bucket.
• D
  1. Use a dual-region Cloud Storage bucket with turbo replication enabled.

Explanation

Option A is correct because a dual-region Cloud Storage bucket provides geographic redundancy - if one region fails, data remains accessible from the other - and critically, the Pub/Sub topic's 1-day message retention acts as the recovery mechanism: when the outage resolves, the Beam pipeline can seek back and replay up to 24 hours of messages, easily satisfying a 15-minute RPO without needing turbo replication.

Option C (regional bucket) is wrong because a single-region bucket becomes entirely inaccessible during a regional outage - there's no failover, so writes are lost and unrecoverable from storage. Option D (dual-region + turbo replication) is wrong not because it wouldn't work, but because it's unnecessary: turbo replication guarantees 15-minute cross-region sync for newly written objects, but since Pub/Sub retention already covers replay well beyond 15 minutes, paying for turbo replication adds cost without solving a real gap.

Memory tip: Ask yourself "Can I replay from the source?" - when the answer is yes (Pub/Sub retention ≥ RPO), standard dual-region storage is sufficient. Reach for turbo replication only when your source data is ephemeral and you must rely on the storage layer itself to meet your RPO.