Which messaging style?

When one system needs to tell another something, there are four common ways to do it, and most systems use more than one. Answer these questions about one specific interaction, such as “the order service tells the warehouse to ship an order”, to see which style fits it.

1 of 7Does the sender need a result before it can continue?

Yes, immediately (for example, to show the user)It needs to know eventually, not right awayNo; it is announcing that something happened

2 of 7How many systems need to act on each message?

Exactly oneA few, known todayMany, and more will be added later

3 of 7Will consumers need to re-read past messages, for example to rebuild data or add a new consumer?

NoOccasionally, for recoveryYes, it is a core need

4 of 7Does the order of messages matter?

NoYes, for the same customer, account or orderYes, globally for everything

5 of 7What volume do you expect at peak?

Low: up to hundreds per secondModerate: thousands per secondHigh: tens of thousands per second or more

6 of 7Must the sender keep working when the receiver is down?

No, it can fail tooYes

7 of 7What kind of processing happens on receipt?

A quick lookup or calculationA slow job: generating a document, calling a partner, sending emailUpdating other systems' copies of the data

Show my recommendation

---

Learn more in messaging, event-driven architecture and orchestration vs choreography.