What is Google Cloud Pub/Sub and how does it differ from traditional message queues?

Google Cloud Pub/Sub is a fully managed, real-time messaging service that enables asynchronous communication between independent applications at scale. It follows the publish-subscribe pattern where publishers send messages to topics and subscribers receive messages from subscriptions.

Core Concepts

Topic: A named resource to which publishers send messages. Subscription: A named resource representing the stream of messages from a single, specific topic. Publisher: Application that creates and sends messages to a topic. Subscriber: Application that receives messages from a subscription.

Delivery Models

Pull delivery: Subscriber explicitly calls an API to retrieve messages. Suitable for batch processing and when the subscriber controls the rate. Push delivery: Pub/Sub sends messages to a webhook endpoint. Suitable for real-time processing and serverless architectures.

How Pub/Sub Differs from Traditional Message Queues

Traditional queues like RabbitMQ or SQS use a point-to-point model where each message is consumed by one consumer. Pub/Sub supports fan-out natively – one message can be delivered to multiple subscriptions simultaneously.

Pub/Sub is fully serverless and scales automatically to millions of messages per second. It integrates natively with Dataflow, BigQuery, Cloud Storage, and Cloud Functions for streaming pipelines.

Key Use Cases

Event-driven microservices decoupling. Stream analytics with Dataflow. Log aggregation and metric collection. IoT data ingestion from millions of devices. Triggering Cloud Functions or Cloud Run services on events.