Tinker08:00, prices kept 1 day: 201 stale price reads today.0 from shelves · 15 to the depot · 15 trips
Chapter 3 of 7
How long is it fresh?
The shelves worked: almost every request is now a hit. Then the depot raises the hinge price, and a customer is charged more than the page said.
This chapter: How long should a copy count as fresh?
About this chapter
You will learn
- TTL: how long a copy counts as fresh
- Why a copy can be fresh and still out of date
- Why a shorter TTL trades trips for correctness
Words you’ll meet
- Stale
- Older than the depot’s current version: the copy no longer matches the original.
- TTL
- Time to live: how long a copy counts as fresh before the shelf must fetch it again.
- Fresh
- Within its TTL, so the shelf serves it without asking the depot.
- Expired
- Past its TTL: the next request fetches a new copy.
Step 1 of 4
At 10:15 the depot raises the hinge price. Shelves still hold the old one, now .
Move the clock to 10:15.