At approximately 9:50 UTC (5:50 AM ET) on June 8, 2021, Fastly—a global Content Delivery Network (CDN) provider—suffered a major outage th

Inside the Fastly Outage: Analysis and Lessons Learned

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2021-06-17 19:30:05

At approximately 9:50 UTC (5:50 AM ET) on June 8, 2021, Fastly—a global Content Delivery Network (CDN) provider—suffered a major outage that impacted the sites and applications of its many customers. The outage lasted for about an hour, during which time users attempting to reach impacted sites would have received 501 service unavailable errors, or experienced issues loading content. Although the outage did not fully resolve until approximately 10:50 UTC (6:50 AM ET), some of Fastly’s customers were able to minimize the impact to their services by leveraging alternative providers to deliver content. 

Fastly subsequently issued a statement identifying a latent software bug introduced in a May 12th software update as the root cause. The bug was triggered by a customer updating their CDN configuration — a routine occurrence for CDN customers. While Fastly has not identified the configuration that triggered the outage (as of June 10, 2021), the impact—85% of their service, according to Fastly—was felt globally. 

Read on to learn more about how this outage unfolded and how four different services experienced the outage very differently, or, if you prefer a podcast experience of this same analysis, tune in to this week's episode of the Internet Report, Ep. 40: Fastly's Outage and Why CDN Redundancy Matters .

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