You are developing a globally scaled frontend for a legacy streaming backend data API. This API expects events in strict chronological order with no repeat data for proper processing. Which products should you deploy to ensure guaranteed-once FIFO (first-in, first-out) delivery of data? 

Answer options:

A. Cloud Pub/Sub alone
B. Cloud Pub/Sub to Cloud Dataflow
C. Cloud Pub/Sub to Stackdriver
D. Cloud Pub/Sub to Cloud SQL

D

Reference: https://cloud.google.com/pubsub/docs/ordering