What is Azure Service Bus?
Answer
Azure Service Bus is a fully managed enterprise message broker with message queues and publish-subscribe topics. It provides reliable, asynchronous message delivery between decoupled applications and services. Queues: point-to-point messaging where one consumer processes each message. Supports dead-letter queues for failed messages. Topics and Subscriptions: publish-subscribe pattern where a message published to a topic is delivered to multiple subscriptions independently, each with configurable filter rules. Key features: At-least-once delivery, FIFO messaging, message sessions (related message ordering), scheduled messages, and transactions. Maximum message size is 100KB (256KB for Premium). It is preferred over Azure Storage Queue for enterprise messaging scenarios requiring ordered delivery, transactions, or pub-sub.