Comparison of Windows Azure Storage Queues and Service Bus Queues

Update[01/17/2012]: MSDN now has a comprehensive  list. Click Here

Note: Comparison list is slightly outdated with the new release of Windows Azure SDK 1.5 and as the products evolve.


Windows Azure Storage Queues

Service Bus Queues


Programming Models      
Raw REST/HTTP Yes Yes  
.NET API Yes(Windows Azure Managed Library) Yes(AppFabric SDK)  
Windows Communication Foundation (WCF) binding No Yes  
Windows Workflow Foundation (WF) integration No Yes  
Runtime REST over HTTP REST over HTTPBi-directional TCP The Service Bus managed API leverages the bi-directional TCP protocol for improved performance over REST/HTTP.
Management REST over HTTP REST over HTTP  
Messaging Fundamentals      
Ordering Guarantees No First-In-First-Out (FIFO) Note: guaranteed FIFO requires the use of sessions.
Message processing guarantees At-Least-Once (ALO) At Least-Once (ALO)Exactly-Once (EO) The Service Bus generally supports the ALO guarantee; however EO can be supported by using SessionState to store application state and using transactions to atomically receive messages and update the SessionState. The AppFabric workflow uses this technique to provide EO processing guarantees.
Peek Lock YesVisibility timeout: default=30s; max=2h YesLock timeout: default=30s; max=5m Windows Azure queues offer a visibility timeout to be set on each receive operation, while Service Bus lock timeouts are set per entity.
Duplicate Detection No Yes, send-side duplicate detection The Service Bus will remove duplicate messages sent to a queue/topic (based on MessageId).
Transactions No Partial The Service Bus supports local transactions involving a single entity (and its children). Transactions can also include updates to SessionState.
Receive Behavior Non-blocking, i.e., return immediately if no messages REST/HTTP: long poll based on user-provided timeout.NET API: 3 options: blocking, blocking with timeout, non-blocking.  
Batch Receive Yes(explicit) Yes. Either (a) Implicitly using prefetch, or (b) explicitly using transactions.  
Batch Send No Yes (using transactions)  
Receive and Delete No Yes Ability to reduce operation count (and associated cost) in exchange for lowered delivery assurance.
Advanced Features      
Dead lettering No Yes Windows Azure queues offer a ‘dequeue count’ on each message, so applications can choose to delete troublesome messages themselves.
Session Support No Yes Ability to have logical subgroups within a queue or topic.
Session State No Yes Ability to store arbitrary metadata with sessions. Required for integration with Workflow.
Message Deferral No Yes Ability for a receiver to defer a message until they are prepared to process it. Required for integration with Workflow.
Scheduled Delivery No Yes Allows a message to be scheduled for delivery at some future time.
Authentication Windows Azure credentials ACS roles ACS allows for three distinct roles: admin, sender and receiver. Windows Azure has a single role with total access, and no ability for delegation.
Management Features      
Get Message Count Approximate No Service Bus queues offer no operational insight at this point, but plan to in the future.
Clear Queue Yes No Convenience functions to clear queue efficiently.
Peek / Browse Yes No Windows Azure queues offer the ability to peek a message without locking it, which can be used to implement browse functionality.
Arbitrary Metadata Yes No Windows Azure queues allow an arbitrary set of <key, value> pairs on queue metadata.
Maximum message size 8KB 256KB  
Maximum queue size Unlimited 5GB Specified at queue creation, with specific values of 1,2,3,4 or 5 GB.
Maximum number of entities per service namespace n/a