Why does one cloud outage take down banks, apps and government sites at once?

Because most of the apps, banks and government sites we use are rented from the same few cloud companies, and inside each cloud a few shared pieces hold everything else up. When one of those pieces breaks, thousands of customers fail together, even though none of them did anything wrong. A cloud is simply someone else's computers, and a lot of us rent the same ones.

October 2025 is the clean example. Amazon Web Services reported a disruption in its N. Virginia region (called us-east-1) that started at 11:48 PM PDT on 19 October and ended at 2:20 PM PDT on 20 October. Amazon said the root cause was a latent race condition in the management of DNS, the internet's name directory, for its DynamoDB database service. It left an incorrect empty DNS record for the service's regional address, and the automation failed to repair it. An empty entry means nobody can find the database, so customers and other AWS services that depended on DynamoDB could not connect to it.

The effect reached the high street. According to a GlobalData analyst, Lloyds, Halifax and Bank of Scotland were affected in the UK. The same analyst noted that banks of all sizes around the world have focused on cloud migration, which has been touted as a panacea for the problems of old systems. It does fix many problems, but it also puts many eggs in a few baskets.

It is not only AWS. In July 2024 a faulty update from the security company CrowdStrike crashed roughly 8.5 million Windows systems, in June 2025 Google Cloud had a disruption across its products, and on 20 October 2026 BBC News reported that Revolut, Lloyds Bank and HSBC were among UK services that confirmed disruption when Google Cloud's London region, europe-west2, had problems that Google attributed to a power event at a third-party facility. The pattern is the same each time: a shared dependency fails, and everything standing on it falls over at once.