Azure Service Bus is a cloud-based messaging service providing queues and topics with publish/subscribe semantics and rich features. This fully managed service is available in multi or single tenant configurations with no servers to manage or licenses to buy.

Use Service Bus to:

• Build reliable and elastic cloud apps with messaging.
• Protect your application from temporary peaks.
• Distribute messages to multiple independent backend systems.
• Decouple your applications from each other.
• Ordered messaging scaled out to multiple readers.

Available Tiers:

Premium Tier - The Premium tier of Service Bus Messaging addresses common customer requests around scale, performance, and availability for mission-critical applications. The Premium tier is recommended for production scenarios. Although the feature sets are nearly identical, these two tiers of Service Bus Messaging are designed to serve different use cases.
Benefits of Premium tier are:

• High throughput
• Predictable performance
• Fixed Pricing
• Ability to scale workload up and down
• Large message support

Standard Tier - The Standard tier of Service Bus can be used for relatively smaller production workloads where customers need to build message based applications in a pay as you go model with variable throughputs and latencies.
Some of the attributes of standard tier are:

• Variable throughput
• Variable latency
• Pay as you go pricing
• Limited workload scaling
• Message size upto 256KB