[Turing_Machine]

It's like the levels of caching in a computer.

(just using orders of magnitude for an example, the actual numbers for best efficiency probably aren't quite so nice)

The 1000 most frequently ordered items in a warehouse near your neighborhood. The 10000 most frequently ordered items in a city-wide warehouse. The 100,000 most frequently ordered items in a regional warehouse.

Amazon already has the regional warehouse part.

I'd guess that this might be worth doing even if only the 1,000 most frequently ordered items can get there in 30 minutes, and should definitely be worth doing if you can get the 10,000 most frequently ordered items there in 30 minutes.

[DufusM]

Agree, it could totally work for Amazon Fresh items, say, that are bound to be ordered regularly.

[pilsetnieks]

Plus they don't have to roll out worldwide simultaneously, they can just do a few select cities at first.