Life without cross-service joins
On This Lesson 4 topics
This lesson is planned. The outline below lists the topics it will cover. The full lesson has not been published yet.
In this lesson
replace joins with three techniques.
Planned topics
- API composition: call each service and combine results in a gateway or backend-for-frontend; fine for small result sets.
- Events and local copies: keep a read-only copy of the fields you need, updated by events; it can be briefly stale.
- Denormalize at write time: store a snapshot, e.g. product name and price in the order line.
- Large reporting joins belong in a separate read model or analytics store.
- Accept that each choice trades freshness, coupling, and cost.
Draft outline details
Demonstration
order history screen: orders stores productName and unitPrice snapshots, so no call to catalog is needed.
Check your understanding
Why snapshot price in the order line?
Show answer
The price at purchase time must not change, and it avoids a catalog call.
Practice
Apply this lesson with the module's lab, exercises and quiz.
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