Do you ever wonder how Amazon orders arrive so fast with near-perfect accuracy?

The company's operational excellent is the backbone of Amazon's reputation for outstanding customer service. I recently toured Amazon's ONT2 fulfillment center in San Bernardino, CA to get an inside look at exactly how the company does it.

Here's a quick profile of this particular facility:

Specializes in small and medium-sized items
It's the size of 28 football fields
Employs more than 2,500 people full-time
14 million products are shipped from here
Amazon's oldest fulfillment center in California

The center is called ONT2 after the nearest airport (Ontario, or ONT) with the 2 designating this as the second center in the area.

The tour revealed cutting-edge technology seamlessly blended with smart logistical management. There was even a genius operational practice that was completely counterintuitive.

Pictures weren't allowed inside, but I took good notes on the process required to pick, pack, and ship your order to you.

The Pick Process

This is where the items you order are selected from inventory, or picked, and sent via a conveyor belt to a packing station.

The process is initially quite counterintuitive. Inventory items are stored in seemingly random locations. One inventory bin might contain a stuffed animal, a video game, a protein shake, and a few other mismatched items. Amazon actually does call this "random stow."

Amazon puts items in all these random locations so they can assign individual pickers to tight areas. This minimizes time spent wandering around the warehouse. It also ensures that each picker has roughly the same amount of work.

Computers make this process possible. Pickers are routed by computer to maximize efficiency. (More advanced warehouses eliminate the walking entirely and have robots carry shelves of products to the pickers!)

The pickers in ONT2 push around carts with tote bins and carry around hand-held scanners. The scanner tells the picker what to pick next and where to find it. A series of three bar-code scans ensures pickers select the correct item:

Scan a bar code on the tote bin.
Scan a bar code on the shelf where the item is located.
Scan a bar code on the item itself.

The picker can't continue until these three scans are accurately completely. Once they are, the picker's handheld scanner directs the picker to the next item which may or may not be part of the same order.

The Pack Process

Once filled, pickers load their totes onto conveyor belts. The belts whisk the totes to packing stations where orders are packed for shipping.

Stations are separated into single-item orders and orders with multiple items.

For single-item orders, packers are prompted by computer to select the correct size box and pack the item. A series of scans ensures the correct item goes in the correct box.

For orders with multiple items, packers first sort items from a tote onto a cart with multiple shelves so the items from each order are grouped together. An order might have items delivered via multiple tote bins if it contains items picked by different people. The computer and scanning process keeps everything organized.

Here, I was amazed at the speed at which packers operated. They selected items, assembled boxes (which are stored flat), put in protective filler, and taped each box shut in a matter of seconds.

The Ship Process

Orders are routed from packing stations down a conveyor belt to something called a SLAM machine.

SLAM stands for:

Scan
Label
Apply
Manifest

The machine scans boxes one at a time. A shipping label is then generated and applied.

The boxes are weighed as they travel down this line and the weights are compared to the expected weight for each shipment. If the weight is off, the box is automatically pushed off the shipping line into a quality control station for inspection.

I was lucky enough to see part of Amazon's rigorous quality control methods on display. Operators detected a problem with the SLAM machine where labels were being misapplied. They immediately shut down the entire line and attempted to fix the problem.

The operators quickly isolated the issue to one of two label applicators on the line, so the disabled to problem applicator until a technician could arrive and restarted the line.

From there, boxes are automatically routed by destination and carrier (USPS, UPS, etc.). The boxes travel along conveyor belts until they reach a warehouse bay door where workers load the boxes into waiting trucks.