Why is the internet broken? How one small problem can take down the whole web

It started in a computer in northern Virginia, at around 3am local time. But just a few moments later it was everywhere.

When an Amazon data centre stopped working properly on Monday morning, so did much of the internet. For hours, users were unable to access many of the world’s most popular apps, platforms and services: everything from Snapchat to the UK’s tax authority were down.