The sites were soon up and running after being hit by a brief power outage at one of Amazon.com data centres on the US East Coast.
"The issue has been resolved and the service is operating normally," AWS said.
Amazon said the outage had affected its platform that provides computing capacity to cloud network operated by its unit, Amazon Web Services (AWS).
Office messaging app Slack had said it was experiencing issues with file uploads, message editing and other services.
A major outage in the same region earlier this month brought down streaming platforms Netflix and Disney+, trading app Robinhood as well as Amazon.com Inc's e-commerce website.