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?

Cloud Pub/Sub provides an asynchronous messaging service that can handle global scale and deliver messages at least once. However, Pub/Sub alone does not guarantee strict chronological order or exactly-once processing. To achieve guaranteed-once (effectively-once) FIFO delivery, you need a processing layer like Cloud Dataflow. Dataflow, built on Apache Beam, can process streams of data from Pub/Sub, apply windowing and stateful processing to ensure chronological order and deduplication, and then deliver the refined data to the backend. Cloud Pub/Sub alone would not guarantee FIFO or exactly-once delivery. Stackdriver (now Cloud Monitoring and Cloud Logging) is for monitoring and logging, not data processing. Cloud SQL is a relational database, suitable for structured data storage, but not for real-time stream processing with FIFO and exactly-once guarantees.