What is Cloud Pub/Sub?
Answer
Cloud Pub/Sub is GCP's fully managed, globally distributed message streaming service. It provides durable publish-subscribe messaging at massive scale. Topics: publishers send messages to a topic. Subscriptions: subscribers receive messages from a topic. Two delivery types: Pull (subscriber pulls messages) and Push (Pub/Sub pushes to a HTTPS endpoint). Key features: At-least-once delivery with acknowledgement-based exactly-once semantics available. Ordering: message ordering keys ensure ordered delivery per key. Dead letter topics: handle unprocessable messages. Retention: up to 7 days. Pub/Sub is the backbone for event-driven architectures and decoupling microservices on GCP — commonly used to trigger Cloud Functions, feed BigQuery streaming inserts, and connect to Dataflow pipelines.