
Notes on a tour of an Amazon distribution facility (2014) - scmoore
https://docs.google.com/document/d/1F12fyVF0PO2fSmkOI2_R1IFigTaznaertxiVXlEbas4/edit
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Animats
That's a old manual Amazon facility. The newer ones use Kiva robots to bring
the shelving units to the pickers, rather than the pickers going to the
shelving units.

The manual system isn't that different from the Sears "schedule system"
introduced in 1908.[1] Note the line "pickers don't necessarily pick items for
a single or even complete order." That's crucial. Orders are split apart and
combined pick lists generated. Picked items then flow towards order assembly
stations, which Amazon calls "sort". At any one time, some maximum number of
orders are in progress, limited by the number of output boxes at order
assembly. Amazon does this with computers; Sears did it with clerks and pick
slips, with Sears giving each order an assembly bin for a fixed number of
minutes.

Separating picking from order assembly and inserting a sort phase reduces the
order of the problem. Picking N orders from M items individually means O(N ×
M) cost, because as inventory becomes larger, the pickers travel more
distance. With separate picking and assembly, performance is something like
O(log(M) × N) cost, because each picker works in a limited area. That was
Sears' big breakthrough.

[1]
[https://news.google.com/newspapers?nid=1734&dat=19721006&id=...](https://news.google.com/newspapers?nid=1734&dat=19721006&id=bXkcAAAAIBAJ&sjid=AVIEAAAAIBAJ&pg=3170,3159101&hl=en)

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EGreg
By the way, wouldn't segways bringing people to the shelves have to expend
less energy and be more efficient than kiva robots bringing shelves to the
people?

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rgbrenner
Hmm.. don't know why asking a question deserves a downvote.

I think you're right that it would be more energy efficient -- since a human
weighs less than a rack full of goods.

But energy, compared to the other costs, is a fairly small component of costs.

The bigger question is whether a person is cheaper than a machine.

A few years ago before Amazon bought Kiva, they would sell a complete setup
for a large warehouse for $15-20m for 1000 robots. This included a lot of
setup, but even if we assume it's just 20m/1000 robots = $20,000 each.

So for $20,000 you can get a robot that will work 24/7 for a few years. Lets
pretend the kiva robots are completely junk after 3 years. That's under
$7000/yr.

Obviously, that's going to be tough to beat with a human. But for comparison,
lets assume a person gets paid federal minimum wage ($7.25/hr), there's no
overhead, no management, healthcare, never gets sick, etc. That equals
$15000/year. But that's only for 40 hours a week x 52 weeks/year. So really,
we'll need 3 people.. so $45000/year. (EDIT: I forgot about weekends, which is
another 48 hours. So really, we need 4 people, or $60,000/year.)

Considering that humans are so much more expensive than a kiva robot, the
increased energy compared to segways doesn't really effect the outcome. It's
clearly cheaper to use robots and simply pay for the increased energy usage.

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Lunarsm
Despite popular belief, most Amazon facilities do NOT use kiva robots. The
fulfillment center would have to be completely rebuilt on the inside to
accommodate them. Heck, even some new facilities still don't use them. I work
over at Amazon in one of their largest fulfillment centers in the USA. To
answer your question regarding where a tote is sent in the facility is simple.
During each shift, there are any number of queues open (usually about 5). When
receiving an item from DA, we will scan an item into a tote and the computer
determines, based on the size of the items, where in the facility it needs to
go (library, or library deep). Aside from a few exceptions, most items are
randomly stowed. The stowers all have a rate, and because of that, will find
whatever space fits their needs. Pallet mass (items with a lot of the same
quantity to fill a pallet) is checked regularly and pulled from the regular
shelves and sent to a sorting area (at least that's what they started doing at
my FC) where it can be stowed somewhere in "pallet land." Try not to think too
much into where items are stowed, it is pretty much a clusterf*ck across the
FC.

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minthd
How does the work for stowers is arranged ? do the computer give them specific
sets of items to stow ? or is arranged according to the order the goods arrive
?

And what is this pallet land ? what's the benefit?

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Lunarsm
Work is arranged by what truck is being processed, we attempt to follow FIFO
as much as possible. Queues are determined, to the best of my knowledge, by
which area of the FC has the most space (but they probably do it arbitrarily,
I'm not in charge of any of that, so I don't really know their method). When a
truck is being received, all cartons will be placed inside totes (or "juice
carts") and sent up to the queues (there's usually only a couple queues that
are "dropping" totes). Stowers are advised to take the totes, which are placed
on u-boats, by using the FIFO method. Stowers are not given specific sets of
items to stow; they only stow what's given to them.

Pallet land is the part of the FC for products we carry in large quantities
(i.e. enough to fill a pallet, quarter pallet, or half pallet). Pallet land is
just a nickname we give part of the pallet area. We also have a 3-story rack
area full of pallets (at my FC). Some items we have on pallets include some
Starbucks, Sonicare, and Darth Vader costumes (omg we have so many).

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michaelbuckbee
The thing I took away from this was mistake minimization. As shipping the
wrong item likely results in a mess of expensive actions down the road, it is
much much better to make sure that the right item is shipped the first time.
To this end they are willing to shuffle their entire warehouse just to prevent
similar items from being set next to each other.

~~~
minthd
I don't think it's really random.Since it's dictated by the computer, even
though it looks random, i'm sure there are some patterns in the order(for
example there are items that statistically sell together) ,But maybe they keep
it as a trade secret , only to be known by a small group of developers and
managers.

~~~
Zombieball
To quote Lunarsm below:

> Aside from a few exceptions, most items are randomly stowed. The stowers all
> have a rate, and because of that, will find whatever space fits their needs.

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Zombieball
This is a pretty great description (disclosure: I currently work at Amazon
writing software used inside the Fulfilment Centers). I think an important
point is there is big variance between facilities throughout the network. For
instance, the use of Kiva robots as mentioned by others here. Meaning if you
were to go on tours of other facilities you would definitely see new things at
each (and of course many similarities).

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marincounty
As I read through the notes, the one thing I really liked was the 4 day work
week. Three days off just makes sense? I belonged to a union, and we had the
opportunity to work 4 10hr. days, and the members voted it down. I still don't
know why they voted it down.

~~~
johnpowell
I worked in a wafer fab for a summer and we did four 12 hour days and then
three days off. And then three days of work and four off.

It was by far one of my favorite schedules. I rode my bike to work and that
was about 45 minutes each way and when you add in the time it takes to get
ready for work it was nice to only have to do that 50% of my days. And with
four day breaks I was able to really get into projects or go camping for a
long time.

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pencerw
All, thanks so much for the comments. We wrote this up so long ago; it's
really interesting to get feedback now.

FWIW, The Infrastructure Observatory is working on more tours like this one,
mostly in the NYC area. If you want to get involved (or have an idea for a
tour that we should organize), get in touch at
[http://infraobservatory.com](http://infraobservatory.com) or @NYInfraObserve
on Twitter.

-Spencer

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veidr
Vaguely interesting, as I suppose a similar tour of, say, a Wal-mart or FedEx
logistics center might be.

Bonus quote: "Our tour guide used an iPhone, but claimed he’d use a Fire if he
wasn’t locked into his carrier."

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omarchowdhury
Does anyone know any good resources/ books on the logistics of setting up and
running a fulfillment/distribution facility with the latest tech?

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confiscate
Pretty cool stuff

I wished they would add a diagram, even if it's just hand-drawn. It's would
have been much easier to visualize, especially the detailed parts.

Also the naming is sometimes inconsistent across the different authors. e.g.
Sometimes folks are called "associates", sometimes "sorters". It got confusing
quickly. Would be nice if the naming was clearer

~~~
tajen
On a side note, there are languages such as French where repeating a word is a
proof of bad style (and possibly lack of culture from the author), and others
like Swedish (e.g. the Millenium books) where repeating is an appeasing
regularity.

~~~
radicalbyte
British English at least is in the "don't repeat" group.

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pervycreeper
He doesn't specify exactly how cubbies are selected at the "inbound" stage,
beyond saying it's random. I assume it's left up to the associate's own whims
and judgements? I imagine the "no identical items in adjacent cubbies" rule
improves the potential for picking the same item in parallel while preventing
too much concentration, improving availability from different locations. I
wonder what other constraints they are given for this stage.

~~~
Lunarsm
It is indeed quite random. Each stower has a rate, and in order for us to make
that rate, we can stow in almost any bin. Some other constraints include using
the smallest bin possible for each item and not stowing heavy items up high
(the scanner restricts stowing "heavy" items up top).

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contingencies
PDF @
[https://docs.google.com/document/export?0=mp&1=ws&2=print&3=...](https://docs.google.com/document/export?0=mp&1=ws&2=print&3=1&format=pdf&id=1F12fyVF0PO2fSmkOI2_R1IFigTaznaertxiVXlEbas4)

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tarekkurdy
Looks like initial notes for an IE Analysis. Pretty good for retrospective.

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BorisMelnik
I have no skin in this game and really don't know much about what is going on,
but really appreciated that rundown. I've always wanted to know what goes on
inside these places.

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sengork
And something unrelated I've learnt about Google Docs:

"Wow, this file is really popular! Some tools might be unavailable until the
crowd clears."

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veidr
Yep that was interesting. I am part of a Google Apps trial at work, but we
don't have the resources to stress test it so I have never seen it under large
simultaneous load (seemed to handle it fairly well though).

