What happens after an online order is placed?

1. Leo and his dad choose a toy robot in an online shop and press Buy. No robot moves yet. What leaves the tablet is a message, called an order: who wants what, and where to send it.
2. First the shop's computer checks its stock list. It shows three robots left. The computer saves one for Leo, so nobody else can buy that same robot. Now the list says two.
3. The order arrives at a warehouse as a pick list. Every shelf has an address, like A3. A picker walks there with a cart and scans the shelf's code. Beep! The scanner agrees: this is the right item.
4. At the packing table, the robot goes into a box that is just big enough. Paper padding stops it from rattling. The box is taped shut, and a printer makes a label with Leo's address and a barcode.
5. A truck collects the parcel with hundreds of others and drives to a sorting center. Machines there read each label and send each parcel toward the right town. A smaller van takes Leo's parcel on the last part of the trip.
6. The van stops at Leo's house. The driver scans the label one last time, and the shop's computer marks the order as delivered. A list on a screen has become a robot in Leo's hands.

This is a small warehouse seen from above. Tap each part to find out what it does for your order.

• Order screen. The screen shows the order as a pick list: each item, and the shelf where it lives. A tick appears when the item is in stock.
• Shelves with addresses. Each shelf space has an address, like A3: row A, place 3. The computer remembers which item lives at each address and how many are left.
• Handheld scanner. The picker carries a scanner. It reads the code on the shelf and beeps if this is the right item. It also tells the computer that one has been taken.
• Picking cart. Picked items ride in a box on the cart, called a tote. One tote holds one order, so items for different people do not get mixed up.
• Packing table. At the packing table the items are checked, put in a box that fits, and padded so nothing breaks. Then the box is taped shut.
• Label printer. The printer makes a shipping label: Leo's address for people to read, and a barcode for machines to read.
• Loading dock. Finished parcels are loaded onto a truck at the loading dock. The truck leaves at a set time, so orders placed early in the day can often go out the same day.

Place the order, then pick each item from its shelf, pack it and send the truck. After that, set the robots to "None left" and order again. What happens?

Experiment: The stock list says there are no robots left. What happens when you place the order?

1. Place the order while robots are in stock, and fill it all the way to the truck.
2. Start a new order and choose "None left".
3. Place the order again and see where it stops.

What we found: With robots in stock, the order flows through every step: stock check, pick, pack, ship and deliver. With none left, it stops at the very first step. The shop tells you right away instead of sending a picker to an empty shelf.

Turn on JavaScript to try it yourself.

The pictures are gone: only shelf addresses are left. Read each address on the list, pick from the right shelf, then pack and ship. Fill two orders.

When you press Buy, nothing moves at first except information. Your tablet sends the shop an order: what you want, how many, and where to send it. The shop's computer keeps a stock list that counts every item in its warehouse. It checks that your item is there and saves one for you, so the same toy is not sold twice.

Next, the order goes to a warehouse, which is a huge building full of shelves. Every place on a shelf has an address, such as A3. The computer makes a pick list that says which address to visit for each item. A person called a picker, or sometimes a robot, goes to each address. A scanner reads the barcode there and beeps to say "yes, this is the right one".

At a packing table, the items are checked again and put in a box that is just the right size. Padding keeps them from breaking. A printer makes a label with your address and a barcode, and the box is taped shut.

A truck carries the parcel, with many others, to a sorting center. Machines read the labels and send each parcel toward the right town. A local van makes the last part of the trip to your door. Each time the label is scanned, the computers learn where your parcel is. Always order online together with a grown-up.

Key words

Order

A message that says what someone wants to buy, how many, and where it should be sent.

Stock

The items a shop has ready to sell. The stock list counts how many of each are left.

Warehouse

A large building where goods are stored on shelves until they are ordered.

Pick list

The list a picker follows: each item in an order and the shelf address where it is kept.

Shipping label

The sticker on a parcel that shows the address and a barcode that machines can read.

Last mile

The final part of a parcel's trip, from the local depot to your door.

Check your thinking

1. What is the first thing the shop's computer does with your order?

   Show the answer

   It checks the stock list and saves the item for you. The stock check comes first. There is no point in sending a picker if the shelf is empty.

2. Why does every shelf space in a warehouse have an address like A3?

   Show the answer

   So that the computer can tell the picker exactly where each item is. With an address for every place, the stock list can say not just what there is, but where it is.

3. The scanner beeps a warning at a shelf. What has most likely happened?

   Show the answer

   The picker is at the wrong shelf, so the item would be wrong. The scanner compares the shelf's code with the pick list. A mismatch is caught on the spot.

4. Why do parcels ride together on a big truck before they go onto small vans?

   Show the answer

   Carrying many parcels together for the long part of the trip saves fuel and time. One truck full of parcels uses much less fuel than hundreds of separate trips.

5. The stock record says 1 robot, but the bin is empty. What should happen?

   Show the answer

   The record is corrected and the customer is told, because data and shelf no longer agree. The count is only a model of the shelf. When they disagree, the real shelf wins: the record has to be fixed and the order held or changed.