How a tiny bug spiraled into a massive outage that took down the internet

At a high level, Amazon's Monday outage stemmed from two programs competing to write the same DNS entry at the same time. webphotographeer/iStockphoto/Getty Images

A massive AWS outage Monday that brought down some of the world’s most popular apps and services all started with a glitch.

The bug – which occurred when two automated systems were trying to update the same data simultaneously – snowballed into something significantly more serious that Amazon’s engineers scrambled to fix, the company said Thursday in a postmortem assessment .

The massive cloud service’s outage meant people couldn’t order food, communicate with hospital networks, access mobile banking, or connect with their security systems and smart home devices. Major global companies, including Netflix, Starbucks