What happens when you click buy on Amazon

There are moments in life where the sheer scale of something knocks you off your feet: The Pyramids at Giza, Machu Picchu in Peru, and little known to some, the Amazon Fulfilment Centre just off the M1.

Chances are, you don’t have a brick from one of the ancient wonders in your house. However, you might have part of the Amazon fulfilment centre wrapped and sitting under your Christmas tree. So how did it get there? Read on to find out your present’s journey from its 550,000 sq ft home to your front door.

Stocking up

Welcome to the world of the Amazon Fulfilment Centre. It's a strange world full of unusual habits and procedures. The first, before you can enter the world of 10,000 Kindles, is to hand over the serial number of absolutely everything you have on your person that Amazon might sell.

The danger is that your stuff might end up being shipped out should you lose it. Serial numbers stop your things getting mixed up with what Amazon owns.

A brief step through security and you are in to the first part of Amazon’s postage process: the inbound dock. Before anything can be shipped out to customers, the stock itself needs to come into Amazon’s warehouse.

The Fulfilment Centre you see pictured here is one of eight dotted across the UK. It is however dwarfed in size by the one million square foot structure located in Scotland.

Between them, Amazon juggles stock around various regions of the country in order to speed up postage. Stock can be ordered in from all around the globe, hence the reason why items on Amazon have varying delivery times.

Around Christmas, Amazon peaks at 2.1 million items shipped in 24 hours across the UK, weighing in at total of 1124 tonnes: that’s a lot of Christmas presents.  But it's peanuts when you compare it to the job the Royal Mail does at Christmas, which at peak times can be hauling over 50 million items a day.

Whichever way you look at it, that’s a lot of stock and it all needs to be sorted and shipped out in the speediest way possible. To do this, Amazon has constructed a hugely efficient conveyor system and its journey starts at the inbound dock.

Stock is lifted off palettes and placed the conveyor belt, where product checkers inspect every item at six different points to ensure it is the right item and isn’t damaged.

This stock is then given a unique barcode and placed into a yellow box to be carried off and put in storage until it is ordered. This barcode is where Amazon’s true efficiency lies, as it enables a computer system to track it throughout the whole packing to postage process.

Stock from these yellow boxes is placed at random throughout a five-floored set of corridors. Why at random? Because it entirely eliminates human error. This way nothing similar can ever get mixed up and placed into the wrong package.

So you won't be receiving Star Wars Episode II instead of Episode III, because they're sitting next to each other on a shelf. Instead, next to one Star Wars DVD might be a box of Lego. Shelf-stackers scan a barcode next to the stock and its exact location is then mapped by a computer. This is stored and used to build up shopping lists for product pickers.

Let’s go shopping

These shopping lists are placed in the quickest order possible by product location, so each product picker spends the least time walking and more time getting products.

Here is where your clicking "buy" really makes a difference. Whatever you purchase through Amazon, it will end up on one of these shopping lists. Someone, somewhere, in one of eight Amazon Fulfilment Centres, is literally doing your shopping for you.

Everything they pick is scanned and placed into orange boxes to be posted out. The orange colour differentiates it from stock coming in. These boxes are then placed back on to the mega-conveyor belt and sped off to the next and final stage in the Amazon process.

As a brief aside, we cannot even begin to explain the scale of these storage aisles. In the space of 10 minutes walking around them we saw more Kindle Fires than we knew existed, a toy of the car from Blade Runner (which we have subsequently ordered) and enough Skylanders to make any kid cry.

That’s a wrap

Next comes the wrapping and packaging of your items. Every product is scanned and marked by size and then linked up with a specific shape of Amazon packaging.

Next time something gets shipped to your house from Amazon, look for numbers on the box such as C4 or C2. These numbers tell the product packers which box will fit what item, with the aim of eliminating as much waste as possible.

At those point, packages still haven’t had an address stamped on them. This is the second to last step in the whole process. Placed on to a conveyor belt in the same order the items came in, each box is still connected to its barcode, so the computer system knows exactly which address to stamp it with.

The conveyor belt goes through a terrifying area called the "slam". Sitting above the packaging lines, here each box has its barcode scanned and the relevant address is literally slammed on to the top of it by a machine. It is also weighed to make absolutely sure it is the right thing going to the right place.

After being slammed, items go onto a fast-moving conveyor ready to be posted out. This conveyor travels through a vast number of chutes, each of which corresponds to a postcode or delivery method. Boxes are tipped off the conveyor belt and down the chute at exactly the correct moment.

Finally, after its lengthy journey, your purchase is loaded on to the relevant lorry and shipped off to your home.

In this final step is where Amazon’s true efficiency genius lies: the entire process works backwards. Amazon knows when every parcel delivery company, Royal Mail included, will be collecting. It links this to your order and then ensures that it is picked at exactly the right time of day, so it will be ready to go into the van the moment it is dropped from the delivery chute.

As for the journey from there, by truck onwards, well that's all down to matters beyond the Fulfilment Centre and beyond our tour of Amazon too. With any luck, there'll be no manic snows this year nor anything else to get in the way of this finely honed process of click to doorstep. The only tough part is choosing the right presents.