What is Pub/Sub?
Publish/Subscribe — a messaging pattern where message senders (publishers) broadcast messages to topics, and interested receivers (subscribers) listen to those topics, enabling loose coupling between systems.
Understanding the Details
Pub/Sub extends the message queue concept with topic-based routing. Publishers send messages to topics without knowing who will receive them. Subscribers express interest in topics and receive all relevant messages. This decoupling means publishers and subscribers can be added, removed, or modified independently. Multiple subscribers can receive the same message, enabling fan-out patterns where one event triggers multiple actions. Google Cloud Pub/Sub, Amazon SNS, and Redis Pub/Sub are common implementations. For SaaS architectures, Pub/Sub patterns enable clean event-driven designs: when a customer signs up, the signup event publishes to a topic, and separate services handle welcome emails, analytics tracking, CRM creation, and onboarding triggers independently.
How It Works in Practice
Event fan-out
A 'new customer' event publishes to a topic. Separate subscribers handle welcome email, CRM record creation, analytics tracking, and Slack notification.
Real-time updates
When data changes in one service, it publishes an update. All interested services receive the change and update their local state.
Audit logging
Every significant action publishes to an audit topic. A logging service subscribes and writes a complete audit trail without coupling to business logic.
Why It Matters
Pub/Sub patterns enable clean, maintainable architectures where adding new functionality doesn't require modifying existing services. This is foundational for scalable systems.
What People Often Get Wrong
Pub/Sub and message queues are the same. Actually, Pub/Sub supports multiple subscribers per message while traditional queues deliver to one consumer.
Pub/Sub is only for large-scale systems. Actually, even small applications benefit from Pub/Sub patterns for clean separation of concerns.
Messages in Pub/Sub are always delivered instantly. Actually, delivery latency depends on the implementation and can range from milliseconds to seconds.
How We Handle Pub/Sub
We design event-driven architectures using Pub/Sub patterns, enabling clean service decoupling and easy addition of new functionality without system-wide changes.
Related Terms
Common Questions
Need Help With Pub/Sub?
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