The queue was in order. Your workers were not.
A customer paid $120 for an item they removed, and Service Bus did nothing wrong.
What you'll learn
- That FIFO delivery and FIFO processing are different things, and concurrency is what separates them
- Why SessionId is a partition-key choice, not a yes/no on ordering
- The one setting that silently gives back the race after you enable sessions
Share this passage
Drawing…
Understand it one step at a time
The short runs these in order in about 50 seconds. Here they are written out — pick any step to jump the short straight to it.
Three events, one cart, in order
Add an item, remove it, then check out — three events on one cart, published to Service Bus in that exact sequence, a second apart.
Frequently asked questions
- Does Azure Service Bus guarantee that messages are processed in order?
- It guarantees delivery order within a session, not processing order. If multiple workers pull messages from the same session concurrently, they can finish out of the order they were delivered in — delivery order and processing order are separate guarantees.
- What does SessionId actually control?
- It's a partition-key decision, not a simple ordering toggle — messages sharing a SessionId are guaranteed to go to the same session-aware receiver, which is what makes in-order processing possible. Get the concurrency setting per session wrong and you can silently reintroduce the race sessions were meant to prevent.
Free app · no app store
These are built for a phone
Every short is drawn at full portrait height, the shape a phone already is. Installed, it opens full-bleed with no address bar across the top — and the whole library reads offline.
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