Staleness budgets
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
state how stale each cached item may be.
Planned topics
- Every cached item gets an explicit tolerance agreed with the business: "category list: 1 h", "price: 1 s", "stock shown: 30 s, checked at checkout".
- The TTL and invalidation design follow from the number.
- Record it next to the cache definition, and monitor the real staleness (age of served entries).
- Where tolerance is zero (checkout total, payment), do not cache; read the source of truth.
Draft outline details
Demonstration
table: item, owner, tolerance, mechanism (TTL, event + TTL, none).
Check your understanding
Where does the tolerance for a price come from?
Show answer
The business decision; engineering then picks a mechanism that meets it.
Practice
Apply this lesson with the module's lab, exercises and quiz.
Marking a lesson complete is optional and you can undo it any time. Your progress stays in this browser.