Millions around the world found themselves unable to access popular services thanks to a Domain Name System issue with Amazon Web Services.

Experts say the incident revealed what can happen when a such a broad spectrum of companies rely on singular cloud provider.

Amazon Web Services, a cloud computing service run by Amazon, experienced a significant outage that disrupted numerous websites on Oct. 20.

The outage affected websites like Coinbase and Fortnite, and disrupted services like Signal, Zoom, and Amazon's own products, including Ring.

In making sense of all the hullabaloo, cybersecurity expert David Kennedy just dropped a curt and pertinent take on the AWS outage.

Amazon Web Services (AWS) had a bad day. That's how the boss of another big US tech firm Cloudflare put it – probably feeling very relieved that Monday's outage, hitting over 1,000 companies and affecting millions of internet users, had nothing to do with him.

A Domain Name System error that originated from Amazon's largest and oldest data center took down major sites Monday. The outage has been resolved.

The outage underscored a central trade-off of cloud computing: while it lets businesses deploy global services without maintaining vast infrastructure, it concentrates risk. A problem in a single region—like Northern Virginia—can cause widespread, simultaneous outages for unrelated companies worldwide.

Since a large portion of the internet depends on AWS, the outage cascaded across major firms in disparate industries, leaving some people unable to access airline information or make everyday purchases, Qi Liao, a professor of computer science at Central Michigan University, told ABC News.