An UPDATED Brief Primer on Amazon's Distribution Network, Part 1 of 2
New Year, New Primer, New Map
Last year I put together what I thought would be an evergreen brief primer on Amazon’s Distribution Network that I’d update from time to time with new data. As I did so, and as I’ve investigated the company since then, I realized that a new primer and map were called for, given how both the company and my understanding of it have changed in the meantime. You can still access the old primer here.
This new one, and the associated map, are updated to the best of my ability as of the present—May 2025. These are not facilities that are planned or in the works, but a snapshot of actually existing and functioning Amazon facilities at present. It’s going to be in two parts because it’s significantly longer than the last one. In this first part, I’ll cover Inbound Cross-Docks and Fulfillment Centers; everything else will be in Part 2.
The map’s a little overwhelming to go through as a whole, so in the following, I’ll use the Los Angeles/Inland Empire region as an example. In addition to providing a little more space than the larger east coast markets, which are so closely packed that it can be difficult to make out what’s going on, this area is also of overriding economic importance given the volume that runs through the Ports of Los Angeles and Long Beach and the vast tracts of warehouses of the Inland Empire (tracked here by Radical Research).
1. Inbound Cross-Docks (Purple)
The first step in the Amazon supply chain is the inbound receiving network, made up of Inbound Cross-Docking Facilities (IXDs). These facilities are naturally close to ports and rail yards. Goods are delivered to Amazon for distribution in various forms, and the whole purpose of the IXDs is to prepare items for the Fulfillment Centers (FCs), which are the next step in the chain. The FCs are meant to be highly efficient “just-in-time” environments; inventory is not meant to be there for more than a week. Thus IXDs act as sorting buffers so that FCs are not overwhelmed. They have typically employed between 2000-2500 people, though the new NIXDS (more below) might employ more.
“Cross-docking” is a kind of anti-warehousing arrangement pioneered by Walmart wherein bay doors are on both sides of a facility: container loads are backed into one side, and then transloaded into full truckloads on the other side. Thus, traditionally IXDs were not intended to be like the enormous holding facilities that, for instance, Walmart has built out in its import distribution centers.
However, in 2024, Amazon completely redid its inbound network with the creation of National IXDs, or NIXDs (the NIXDS are labeled on the map). These buildings are meant to be more like Walmart holding facilities, and are much larger (1 million square feet) than the average IXD (around 600,000 square feet). They are now the first step in the chain, and they feed the regional IXDs (the existing IXD network), though I’m sure plenty of stuff still goes to the regional IXDs first.
The NIXDs serve multiple ends of the company: in 2023, Amazon launched Supply Chain by Amazon, the company’s effort to become an end-to-end logistics service for its vendors: they pick up inventory directly from seller manufacturers, cross borders, store and replenish inventory—they do it all. It poses a massive challenge to larger retailers, in that the smaller foreign vendors that typically deal with a Walmart or a Target can compete in the American market more directly. The larger NIXDs can serve to handle the extra inventory that Supply Chain by Amazon requires.
The NIXDs also serve Amazon’s regionalization strategy: after the pandemic splurge, Amazon realized it needed to rein in shipping costs, and so divided up the United States into eight regions. The company aims to have as many orders as possible fulfilled by stock within any given region, so as to cut down on the distance a package needs to travel, and more specifically to cut down on its air cargo volume (by far the most expensive way for a package to travel is on a plane).
Previously a vendor might ship its goods to one IXD, which would then disburse to nearby FCs, which in turn would have to find a way to get a package on one side of the country to the other side, if need be. The NIXDs minimize long range FC fulfillment by parsing inbound goods amongst regional IXDs around the country, spreading goods around the country on the front end (when they can move them about in full truckloads and more slowly) rather than having to deal with long range fulfillment on the back.
The NIXDs have accounted for by far the most amount of recent growth in Amazon’s distribution network, being about 23 of the 35 million square feet that Amazon added in 2024.
As you can see here, all of the IXDs around Los Angeles are in the Inland Empire, and there is a preponderance of them there - roughly 1/8 of all Amazon IXDs. This speaks to the enormous importance of the ports of Los Angeles and Long Beach, through which roughly 40% of all containerized imports in the United States flow. After arriving at the ports, roughly 30% of goods are brought through the Alameda corridor (an exclusive cargo rail line) and then to the warehousing sprawl of the Inland Empire; the remaining 70% go there by truck.
2. Fulfillment Centers
Amazon is perhaps best known in popular and academic accounts for its awe-inspiring FCs. It even gives free tours of these facilities, understanding how associated they are with the Amazon brand.
FCs are generally located in suburban/exurban areas and near major highways and parcel hubs. They come in a great variety, and one big difference between this Amazon primer and the one I put together last year is that I’ve broken these different FCs into different map layers, recognizing that it doesn’t make sense to lump them all together in one layer.
2a. Sortable Fulfillment Centers (Blue)
The Sortable Fulfillment Centers handle anything below certain dimensional and weight limits (~20 pounds). In this sense, Amazon does not care what an item is so much as whether it is conveyable and processable within their sortable facilities.
Some of the FCs listed in this layer are traditional sortable facilities, meaning that they are not subject to the robotics wizardry of Amazon Robotics Sortable Fulfillment Centers (ARS FCs), but it is the destiny of all Sortable Fulfillment Centers to become ARS Fulfillment Centers (only a small percentage of Sortable FCs are not ARS FCs), so I have grouped these together. This is because Amazon’s robotics technology is most suitable for sortable item facilities.
The biggest technology win for Amazon has been the widespread adoption of Kivas. The workhorses of ARS Fulfillment Centers are the Hercules Kiva robots, which look like giant Roombas. They move “pods”—giant stacks of inventory weighing up to 2,000 pounds—to and from human stowers and pickers. Hercules robots move around on floors with QR codes every couple feet, which is how they recognize their position and know where to go next. They are generally physically separated from workers by a chain link fence, and only special technicians wearing tech vests that deactivate Hercules robots nearby are allowed behind that fence.
The Hercules has made randomized storage very efficient: in a traditional warehouse, you’d want to keep all the toothbrushes grouped together with other toothbrushes and bathroom items so as to be able to find them easily. At the ARS facilities, new inventory is placed randomly in the stacks carried about by the Kiva robots and bounces around the facility floor. Amazon wants there to be toothbrushes spread throughout the stacks so that when someone orders one, the nearest Kiva robot with a toothbrush in one of its stack’s pods can get to a pick station quickly. It’s a system that would have been barely imaginable just a decade ago.
Amazon has a lot of cool robots. None are as close to important as Hercules. It’s what saves a human being from having to walk a few football fields to sift through items for a particular order. According to Brad Stone in Amazon Unbound, the average pick rate in a Fulfillment Center jumped from 100 items/hour to 300-400 after the introduction of Kiva technology.
Recently, Amazon has invested a great deal in its robotics arm program in an effort to automate away the baseline picking and stowing role. Instead of having human beings “stowing” items in the mesh-band pods carried around by the Kivas and then “picking” them again after an order comes in, they want robotic arms to be doing that work. In 2023, they announced the deployment of the Sequoia system at its SHV1 Fulfillment Center in Shreveport, LA to do just this. Sequoia automates much (60%) of the picking/stowing role, but it requires the installation of new blue bins (they kind of look like milk crates) to operate. Here are those bins:
But just recently they announced Vulcan, a new system that can work with the normal mesh-band yellow pods:
The yellow towers moved around by Kivas are already in most Fulfillment Centers; the blue bins are not. So Vulcan requires both less investment and less operational disruption to deploy than Sequoia - that’s really the key leap here for Amazon. Vulcan’s only being tested at a Fulfillment Center in Spokane for the moment, but its widespread adoption would mean further significant workforce reductions at its sortable facilities.
For the moment, ARS FCs employ about 3,000 people each, though again that number is going to significantly decline over the coming years. Traditional Sortable FCs employ around 1,800 people each, and the “Soft Lines” sortable facilities (those that deal with apparel, bedding, textiles, anything soft) employ around 1,300 people each. Though during peak season, employment numbers might be 50% above normal.
2b. Non-Sort Fulfillment Centers (Dark Blue)
Much less exciting technologically than the ARS FCs are the Non-Sort Fulfillment Centers that deal with larger items (between 20-60 pounds) that are not conveyable/processable within sortable facilities. It’s possible that automation will come for these facilities one day too, but it hasn’t really happened yet. About 900 people on average work at a Non-Sort FC.
2c. Sub-Same Day Fulfillment Centers (Brown)
The Sub-Same Day (SSD) Fulfillment Centers are a growing category of Fulfillment Centers: after the growth of NIXDs and Rural Wagon Wheels (which I’ll cover in Part 2), SSDs were the fastest growing type of Amazon’s facilities in 2024.
They are something of a replacement for the Prime Now service, an ultra-fast Amazon service that shuttered in 2021. But whereas Prime Now hubs were very small (25,000 square feet) and focused on a pretty limited number of items that could be delivered within an hour or two, SSDs are a bit bigger (around 150,000 square feet) and, as their name implies, focused on getting your item their very fast (in less than a day) but not as fast as Prime Now hubs. Items fulfilled at SSDs do not go to separate sortation or delivery facilities but are loaded directly into Amazon Flex drivers’ cars.
The SSDs are made possible by a massive amount of point of sale data and predictive algorithms. In one sense, they are the highest point of evolution of Amazon’s fulfillment network, the whole point of which is to get items as close to where they’re going to be purchased as logistically possible. The NIXDs, regionalization, the sortation network… everything is designed for this one simple purpose: to know something that hasn’t happened yet.
As you might guess, these FCs are much closer to population centers than other FCs, typically nestled along with Delivery Stations. They employ about 500 people each.
2d. XL Network (Red)
Amazon has a dedicated network of facilities, including Fulfillment Centers, Sortation Centers, and Delivery Stations, that deal only with big and bulky items, i.e., things like dishwashers, refrigerators, and other large items that might require installation and removal.
XL facilities are very often co-located, with the fulfillment, sortation, and delivery functions all happening at a single facility. XL Delivery Station codes typically start with an “H”, as regular Delivery Station codes start with a “D.” If XL Delivery Stations are not co-located with XL Fulfillment and Sortation Centers, they are often co-located with regular Delivery Stations.
XL employment levels are much lower than at other Amazon facilities. At the XL Fulfillment Centers, it’s about 275 people on average, and at the XL Delivery Stations, about 40 people.
2e. Fresh Fulfillment Centers (Gray)
These are ambient and cold storage distribution facilities for Amazon Fresh stores. For various reasons detailed here, MWPVL’s Marc Wulfraat believes that Amazon has been slow to develop its food distribution networks, but that “the next tsunami in the food industry will be Amazon.”
2f. Supplemental Fulfillment Centers (Gray)
These Fulfillment Centers are overflow facilities, often only used during peak season.
Items leave the FCs in the very packages that show up in your lobbies and on your doorsteps. To get there, some are injected into the distributional streams of the US Postal Service, the United Parcel Service, and a few regional carriers, but most (let’s say 80%, though that number is growing every day) are handled by Amazon’s own logistics operation. And from the FC, the next step in that chain is generally either an Air Hub or Sortation Center, both of which I’ll cover in Part 2. Coming Soon!
Thanks for this great research! With the Newark air hub called off a few years ago, how you expect NYC supply works? Is it brought through the Port of Newark, trucked to TEB9 (the closest IXD), and brought back to JFK8 and other FCs? Or is it more likely that inbound goods arrive to FCs from Allentown and JFK airports?
did part 2 come out yet?