Google Pub/Sub is a messaging service designed to handle real-time data streaming between distributed systems. It acts as an intermediary, allowing applications (publishers) to send messages to “topics” and other applications (subscribers) to receive those messages via “subscriptions.” This decouples data producers from consumers, enabling scalable and asynchronous communication. For example, a weather sensor (publisher) can send temperature readings to a topic, while a dashboard service (subscriber) pulls these readings from a subscription to display real-time updates. Pub/Sub guarantees at-least-once message delivery and automatically scales to handle high throughput, making it suitable for scenarios requiring reliable data streaming.
A common use case is event-driven architectures. Imagine an e-commerce platform where user actions (e.g., adding an item to a cart) trigger events. Publishers (like the frontend) send these events to a Pub/Sub topic. Subscribers, such as inventory management or recommendation services, process the events asynchronously. Another example is log aggregation: multiple microservices can publish logs to a topic, and a centralized logging system subscribes to process and store them. Pub/Sub also integrates with Google Cloud services like Dataflow for real-time analytics. For instance, a retail company might stream sales data to Pub/Sub, then use Dataflow to compute rolling revenue averages and store results in BigQuery.
Pub/Sub simplifies scalability and fault tolerance. Subscribers can process messages independently, and multiple subscribers can read from the same subscription for parallel processing. If a subscriber fails, messages are retained (up to seven days by default) and redelivered. Push and pull delivery modes offer flexibility: pull requires subscribers to request messages, while push sends them directly to HTTPS endpoints. Developers can also enforce message ordering using ordering keys or route undeliverable messages to dead-letter topics for debugging. By abstracting infrastructure concerns, Pub/Sub lets developers focus on business logic while ensuring reliable, low-latency data streaming across distributed systems.