Beginner LevelSystem Design & Architecture
What is the Publisher-Subscriber (Pub/Sub) pattern?
❓ Interview Prompt: Explain Publisher-Subscriber (Pub/Sub) messaging pattern, message topics, fan-out pattern, and decoupling event producers from subscribers.
The Publisher-Subscriber (Pub/Sub) pattern is an asynchronous messaging pattern where message senders (Publishers) do not send messages directly to specific receivers:
How Pub/Sub Works:
1
Publishers publish messages to named Topics on a Message Broker (Apache Kafka, RabbitMQ, Google Cloud Pub/Sub).
2
Multiple subscriber services subscribe to topics of interest.
3
Fan-Out: When a message is published, the broker automatically broadcasts a copy to ALL subscribed services concurrently!
Code Implementation Example
markdown
Pub/Sub Fan-Out Messaging Flow:
┌──> [Email Service Subscriber]
│
[Publisher (Order Service)] ──> (Topic: 'order_created') ──┼──> [Inventory Service Subscriber]
│
└──> [Analytics Service Subscriber]💡Pub/Sub fan-out architecture broadcasting order events to multiple subscribers.
🎯 Interview Key Takeaway
Use Pub/Sub messaging to broadcast events to multiple downstream consumer services without coupling the producer.
#System Design#PubSub#Messaging#Kafka#Beginner
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