Exam Professional Cloud Architect topic 1 question 102 discussion

I believe the answer is B. "Pub/Sub doesn't provide guarantees about the order of message delivery. Strict message ordering can be achieved with buffering, often using Dataflow." https://cloud.google.com/solutions/data-lifecycle-cloud-platform

B is the answer. CloudSQL is only for storage, to get the messages in order you need timestamp processed in dataflow to arrange them before putting it in any storage volume. The system described is not querying a db it is expecting a stream of messages only dataflow can correct the order. ACID has no value here because the db is not being queried. You'll not find any documentation on pub/sub order being corrected with a db. See notes below on pub/sub and dataflow using timestamps and windows to ensure order https://cloud.google.com/pubsub/docs/pubsub-dataflow

PubSub can only guarantee AT-LEAST-ONCE delivery, so dataflow is required afterwards to clean up any duplicates

Answer is still B (Pub/Sub + Dataflow), because https://cloud.google.com/pubsub/docs/exactly-once-delivery#regional_considerations mentions "The exactly-once delivery guarantee only applies when subscribers connect to the service in the same region. If your subscriber application is spread across multiple regions, it can lead to duplicate message delivery, even when exactly-once delivery is enabled." (so the exactly-once delivery only works regionally, but the question says architect for global) The question's constraint of a globally scaled frontend, means you'll have clients in multiple regions.

"globally scaled frontend" means Dataflow is required. If the clients were in 1 region only pushing messages, then Pub/Sub alone would be the solution. Since there are global clients, this requires Dataflow.

Cloud Pub/Sub to Dataflow because the data is streaming.

https://cloud.google.com/pubsub/docs/exactly-once-delivery#regional_considerations

Google Cloud Pub/Sub now supports message ordering, which ensures that messages with the same ordering key are delivered in the exact order they were published. This feature addresses the requirement for strict chronological order without the need for additional services. Key Features of Cloud Pub/Sub with Message Ordering: Message Ordering: By using ordering keys, Pub/Sub can guarantee that messages are delivered in the order they are published. Exactly-once Delivery: Pub/Sub supports at-least-once delivery and can be configured to handle duplicate messages. Scalability and Reliability: Pub/Sub is a fully managed service that scales automatically and ensures high availability.

A. Cloud Pub/Sub alone Cloud Pub/Sub Ordered Delivery: Cloud Pub/Sub natively supports ordered delivery when using the same ordering key. This guarantees that messages with the same key are delivered to subscribers in the order they were published, preventing out-of-order events. Exactly-once Delivery: Cloud Pub/Sub also offers exactly-once delivery within a region, ensuring that each message is delivered to a subscriber only once.

Pub/Sub provide ordered delivery but doesn't ensure deduplication. Cloud SQL is regional resource and it cant perform custom logic. I go with B

A is correct. While Cloud Dataflow can be used for data processing, it doesn't guarantee FIFO order on its own. Additionally, introducing another processing layer adds complexity and might not be necessary for this specific requirement.

Dont see a need for SQL here as the answer suggests. Option B is more appropriate

B would be correct as pubsub b service might redeliver messages. When you receive messages in order and the Pub/Sub service redelivers a message with an ordering key, Pub/Sub maintains order by also redelivering the subsequent messages with the same ordering key. The Pub/Sub service redelivers these messages in the order that it originally received them.

b, even if pubsub now have exactly-once-delivery this is within a region. question is for a global app. https://cloud.google.com/pubsub/docs/exactly-once-delivery#exactly-once_delivery_2

Answer is B. Key words: globally scaled and ensure delivery only once: Pubsub + Dataflow. If it were only one region, it would be fine to say just pubsub, but it is globally scaled.

B, you need dataflow to deduplicate. Pub/Sub does "at-least" once delivery.

It should be A