Amazon Says ‘Unexpected Behavior’ Caused Huge Cloud Outage

  • Company’s technical statement pledges to learn from event
  • Expert says ‘bad piece of code’ sparked a ‘snowball effect’
Photographer: Jason Alden/Bloomberg
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Amazon.com Inc. said automated processes in its cloud computing business caused cascading outages across the internet this week, affecting everything from Disney amusement parks and Netflix videos to robot vacuums and Adele ticket sales.

In a statement Friday, Amazon said the problem began Dec. 7 when an automated computer program -- designed to make its network more reliable -- ended up causing a “large number” of its systems to unexpectedly behave strangely. That, in turn, created a surge of activity on Amazon’s networks, ultimately preventing users from accessing some of its cloud services.