Invariants across boundaries
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
find the rules that must always hold across services and decide how each is protected.
Planned topics
- An invariant is a statement that must stay true, such as "every captured payment has exactly one order" or "stock is never negative".
- Within one database a transaction can enforce it; across services nothing enforces it by default.
- List invariants by walking a workflow and asking what must be true after each step and after each failure.
- For each, choose: prevent it by design, detect it by checks, or repair it when broken.
Draft outline details
Demonstration
Table: invariant | services involved | enforced by | failure that breaks it. Example: payment captured implies order exists | payments, orders, provider | nothing yet | order insert fails after capture.
Check your understanding
Why do cross-service invariants need explicit design?
Show answer
No single transaction enforces them across services.
Practice
Apply this lesson with the module's lab, exercises and quiz.
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